Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement
I'm not sure if you can have multiple advertise-map for one BGP neighbour ? If you can, then you could have this kind of setup: neighbor COGENT_NEIGHBOUR_IP advertise-map ADVERTISE_WITH_COMMUNITIES exist-map EXIST_ATT_PREFIX neighbor COGENT_NEIGHBOUR_IP advertise-map ADVERTISE_ALL non-exist-map NON_EXIST_ATT_PREFIX I've only set this up for conditional advertisement when a prefix DID NOT exist, so I don't know if you can do both at the same kind and I can't find doco to say either way. There might be some permutation or variation of this command (or in combination with something else) that may help you achieve what you need to. The other tip I can give if you try setting something like this up is to NOT track the default route from ATT. Find a prefix that they use on their core network (ie. an ATT subnet that if you weren't seeing it would mean bad things had happened) and track that one. regards, Tony. --- On Sat, 25/10/08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: From: [EMAIL PROTECTED] [EMAIL PROTECTED] Subject: [c-nsp] BGP Multihomed Selective/Conditional Advertisement To: cisco-nsp@puck.nether.net Date: Saturday, 25 October, 2008, 8:07 AM I have been trying to figure out how to do this and maybe someone will be able to help me out. I have two ISP connections ISP ATT and ISP Cogent. (ISP Cogent)(ISP ATT) | | RO --- R1 ATT would be used for primarily internet and access to our webservers. Cogent would be primarily used to access Cognet's network that use VPN for incoming connections only. I do not want to have other networks besides Cogent's network using this path to access our webserver. I would like to have each other act as a backup for one another. For instance if ATT fails I want everyone on the internet use Cogent to access me. If Cogent fails I want everyone on the internet and the VPN connections on Cogent's network to use ATT. So basically what I was thinking to setup is to accept a default router from ATT and Cogent. Lower the local preference of Cogent and that way I would accomplish using ATT as primary internet access. The tricky part is with Cogent and using then to only access their local networks. Looking through communities I found out Cogent's communities that would not export my route to their peers and keep it internal within their AS. This works fine but the problem now is how do I failover if ATT fails? How do I automatically change my not-export community I'm sending to Cogent to start adverting the route to its peers? I looked at conditional advertisement, I was able to basically send the route map with not-export communities to Cogent if the default route from ATT is present. The problem with this is that once the default router disappears it doesn't advertise anything to Cogent, none of my routes are advertised to Cogent. I'm not sure if I could do this sort of a double condition such as if ATT's default route is present send out to Cogent a route map with prefixes to not-export my routes if ATT's default route is not present sent to Cogent a route map without any communities on my routes Basically I'm trying to figure out how I can have multihoming, but with the constrains that I want 1 ISP to be used for internet and the other to only access their AS, but still have the capability to automatically failover in case one of the circuits dies. Thank you for any input or help. Tom Kacprzyński Network Engineer ___ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/ ___ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement
I'm not sure if I can have multiple advertise-maps also, but can't find any documentation on it either. Does anyone else know? I tried something similar to what you posted: neighbor COGENT_NEIGHBOUR_IP advertise-map ADVERTISE_WITH_COMMUNITIES exist-map DEFAULT-ATT-PREFIX neighbor COGENT_NEIGHBOUR_IP advertise-map ADVERTISE_ALL non-exist-map DEFAULT-ATT-PREFIX but I was tracking for the same route-map DEFAULT-ATT-PREFIX on both, not NON_EXIST_ATT_PREFIX and EXIST_ATT_PREFIX. Do you think that could matter? With the above config it only matched on my first advertise-map and keeps it in withdraw state. The other tip I can give if you try setting something like this up is to NOT track the default route from ATT. Find a prefix that they use on their core network (ie. an ATT subnet that if you weren't seeing it would mean bad things had happened) and track that one. Why do you think a different route be different? The reason I ask is that i'm planning on only getting a default rotue from ATT. Another thing I tried was neighbor COGENT_NEIGHBOUR_IP advertise-map ADVERTISE_WITH_COMMUNITIES exist-map DEFAULT-ATT-PREFIX neighbor COGENT_NEIGHBOUR_IP route-map ADVERTISE_ALL out So the idea was to advertise the route-map once advertise-map withdraws the ADVERTISE_WITH_COMMUNITIES. Coudn't get that to work either. Does anyone know where advertise-map fits with the order of exporting routes? Thank you, From: Tony [mailto:[EMAIL PROTECTED] Sent: Sat 10/25/2008 5:37 AM To: cisco-nsp@puck.nether.net; Kacprzynski, Tomasz Subject: Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement I'm not sure if you can have multiple advertise-map for one BGP neighbour ? If you can, then you could have this kind of setup: neighbor COGENT_NEIGHBOUR_IP advertise-map ADVERTISE_WITH_COMMUNITIES exist-map EXIST_ATT_PREFIX neighbor COGENT_NEIGHBOUR_IP advertise-map ADVERTISE_ALL non-exist-map NON_EXIST_ATT_PREFIX I've only set this up for conditional advertisement when a prefix DID NOT exist, so I don't know if you can do both at the same kind and I can't find doco to say either way. There might be some permutation or variation of this command (or in combination with something else) that may help you achieve what you need to. The other tip I can give if you try setting something like this up is to NOT track the default route from ATT. Find a prefix that they use on their core network (ie. an ATT subnet that if you weren't seeing it would mean bad things had happened) and track that one. regards, Tony. --- On Sat, 25/10/08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: From: [EMAIL PROTECTED] [EMAIL PROTECTED] Subject: [c-nsp] BGP Multihomed Selective/Conditional Advertisement To: cisco-nsp@puck.nether.net Date: Saturday, 25 October, 2008, 8:07 AM I have been trying to figure out how to do this and maybe someone will be able to help me out. I have two ISP connections ISP ATT and ISP Cogent. (ISP Cogent)(ISP ATT) | | RO --- R1 ATT would be used for primarily internet and access to our webservers. Cogent would be primarily used to access Cognet's network that use VPN for incoming connections only. I do not want to have other networks besides Cogent's network using this path to access our webserver. I would like to have each other act as a backup for one another. For instance if ATT fails I want everyone on the internet use Cogent to access me. If Cogent fails I want everyone on the internet and the VPN connections on Cogent's network to use ATT. So basically what I was thinking to setup is to accept a default router from ATT and Cogent. Lower the local preference of Cogent and that way I would accomplish using ATT as primary internet access. The tricky part is with Cogent and using then to only access their local networks. Looking through communities I found out Cogent's communities that would not export my route to their peers and keep it internal within their AS. This works fine but the problem now is how do I failover if ATT fails? How do I automatically change my not-export community I'm sending to Cogent to start adverting the route to its peers? I looked at conditional advertisement, I was able to basically send the route map with not-export communities to Cogent if the default route from ATT is present. The problem with this is that once the default router disappears it doesn't advertise anything to Cogent, none of my routes are advertised to Cogent. I'm not sure if I could do this sort of a double condition such as if ATT's default route is present send out to Cogent a route map with prefixes to not-export my routes if ATT's default route is not present sent to Cogent a route map without any communities on my routes Basically I'm trying to figure out how I can have multihoming, but with the constrains that I want 1 ISP to be
Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement
In this particular setup the router R0 wouldn't be peering with ATT's router, it would get the default router from R1 with is my other router, so I would not get the neighbor down alert. (ISP Cogent)(ISP ATT) | | RO --- R1 Is there a way to use event manager to track a default route with communities set on it or defaul route with next hop to monitor as an event and take action based on that? Thank you, From: Ben Steele [mailto:[EMAIL PROTECTED] Sent: Fri 10/24/2008 8:55 PM To: 'Ben Steele'; Kacprzynski, Tomasz; [EMAIL PROTECTED]; cisco-nsp@puck.nether.net Subject: RE: [c-nsp] BGP Multihomed Selective/Conditional Advertisement Ah my apologies I should have read your original email, your problem is a little more trickier than that. After having read your original one though I believe you could probably do this with an event manager task used to watch logging for bgp neighbour failure you could trigger it to modify your export community and do a clear ip bgp x.x.x.x out Ben -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ben Steele Sent: Saturday, 25 October 2008 10:44 AM To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; cisco-nsp@puck.nether.net Subject: Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement If it's purely just for failover (ie you don't want to get billed for traffic down your failover link while your active is up) then why not just send the community: 174:70 70 Set customer route local preference to 70 This will make them use ATT's path until the ATT link goes down. Ben -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Saturday, 25 October 2008 9:48 AM To: [EMAIL PROTECTED]; cisco-nsp@puck.nether.net Subject: Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement Arie, Thank you for your response. In my situation, where everything is normal, I am actually sending their specific communities for them not to advertise my route to their peers. My only problem is how to change that automatically when my default route from ATT goes away (ATT circuit does down and I'm in a failover situation)? Thank you, -Original Message- From: Arie Vayner (avayner) [mailto:[EMAIL PROTECTED] Sent: Fri 10/24/2008 6:03 PM To: Kacprzynski, Tomasz; cisco-nsp@puck.nether.net Subject: RE: [c-nsp] BGP Multihomed Selective/Conditional Advertisement Tom, Instead of not advertising a certain prefix, there is another alternative using BGP communities which are recognized by your upstream providers. Take a look for what Cogent supports for example (better ask them for the official list...): http://www.onesc.net/communities/as174/ You could play with the local pref communities or the no-export ones Its not the full answer, but just another idea... Let me know if you are still stuck... Arie -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, October 24, 2008 23:07 PM To: cisco-nsp@puck.nether.net Subject: [c-nsp] BGP Multihomed Selective/Conditional Advertisement I have been trying to figure out how to do this and maybe someone will be able to help me out. I have two ISP connections ISP ATT and ISP Cogent. (ISP Cogent)(ISP ATT) | | RO --- R1 ATT would be used for primarily internet and access to our webservers. Cogent would be primarily used to access Cognet's network that use VPN for incoming connections only. I do not want to have other networks besides Cogent's network using this path to access our webserver. I would like to have each other act as a backup for one another. For instance if ATT fails I want everyone on the internet use Cogent to access me. If Cogent fails I want everyone on the internet and the VPN connections on Cogent's network to use ATT. So basically what I was thinking to setup is to accept a default router from ATT and Cogent. Lower the local preference of Cogent and that way I would accomplish using ATT as primary internet access. The tricky part is with Cogent and using then to only access their local networks. Looking through communities I found out Cogent's communities that would not export my route to their peers and keep it internal within their AS. This works fine but the problem now is how do I failover if ATT fails? How do I automatically change my not-export community I'm sending to Cogent to start adverting the route to its peers? I looked at conditional advertisement, I was able to basically send the route map with not-export communities to Cogent if the default route from ATT is present. The problem with this is that once the default router disappears it doesn't advertise anything to Cogent, none of my routes are advertised to Cogent. I'm not sure if I could do this sort of a double condition such as if ATT's
Re: [c-nsp] OSPF over PPPoATM
On Monday 20 October 2008 15:43:03 Marko Milivojevic wrote: Before I accuse intermediate DSLAM filtering them, could you post relevant interface and OSPF process configurations from both routers, please? Marko, Would it be possible for a DSLAM to implement filtering on the AAL5 encapsulated traffic? It would have to decapsulate and interpret UDP/IP packets to do it. Did you experience anything similar? I would point my finger at a IOS bug, however I tried several completely different IOSes on both the termination and DSL box with no change. Anyway, this is the relevant configuration: 7200 PPP terminator: -- interface ATM2/0 no ip address load-interval 30 atm sonet stm-1 atm pppatm passive no atm auto-configuration no atm ilmi-keepalive no atm address-registration no atm ilmi-enable range PPPOA-10 pvc 10/100 10/250 ubr 1000 dbs enable oam-range manage encapsulation aal5mux ppp Virtual-Template1 create on-demand interface Virtual-Template1 ip unnumbered Loopback0 no ip redirects no ip proxy-arp ip ospf message-digest-key 1 md5 7 ip ospf network point-to-point peer default ip address pool adsl ppp authentication pap callin adsl ppp authorization adsl ppp accounting adsl router ospf 9026 log-adjacency-changes area 0 authentication message-digest summary-address 62.212.6.0 255.255.255.0 summary-address 62.212.4.0 255.255.255.0 redistribute connected subnets redistribute static subnets network 62.212.0.0 0.0.31.255 area 0 - gw-dsl#sh ip ospf interface Vi2.21 Virtual-Access2.21 is up, line protocol is up Internet Address 0.0.0.0/0, Area 0 Process ID 9026, Router ID 62.212.3.248, Network Type POINT_TO_POINT, Cost: 100 Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 oob-resync timeout 40 Hello due in 00:00:00 Index 33/33, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 0, maximum is 0 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 1, Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Message digest authentication enabled Youngest key id is 1 2800 DSL Box: -- interface ATM0/1/0 no ip address no atm ilmi-keepalive dsl operating-mode auto pvc 8/35 encapsulation aal5mux ppp Virtual-Template1 interface Virtual-Template1 ip address negotiated ip ospf message-digest-key 1 md5 7 xxx ipv6 enable ppp pap sent-username uli.adsl password 7 xxx router ospf 9026 log-adjacency-changes area 0 authentication message-digest redistribute connected subnets redistribute static metric 200 subnets network 62.212.0.0 0.0.31.255 area 0 - gw-milano#sh ip ospf interface Vi1.1 Virtual-Access1.1 is up, line protocol is up Internet Address 62.212.6.189/32, Area 0 Process ID 9026, Router ID 62.212.3.243, Network Type POINT_TO_POINT, Cost: 284 Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 oob-resync timeout 40 Hello due in 00:00:07 Supports Link-local Signaling (LLS) Index 5/5, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 0, maximum is 0 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 0, Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) Message digest authentication enabled Youngest key id is 1 Bye, -- Daniele Orlandi つづく ___ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement
So what you are saying is that if I use communities to have Cogent prepend the pefix few times, Cogent's routers will ignore the multiple ASN in the path, but when they export it to their peers that path should be longer than the path through ATT because of Cogent's extra ASN in there, correct? But if there could be many Cogent peers closer to Cogent than ATT where with let's say 3 perepended ASNs they still prefere Cogent istead of ATT. So based on the peering on the internet I would create a sort of load-balancing on my links? Thank you, From: Ryan Otis [mailto:[EMAIL PROTECTED] Sent: Fri 10/24/2008 6:29 PM To: Kacprzynski, Tomasz Subject: RE: [c-nsp] BGP Multihomed Selective/Conditional Advertisement If you want the Cogent to act as a failover link, use AS prepending instead of the no-export community. 174:3003 should be enough to cause nearly all other ISPs to use the ATT link, leaving only Cogent using the Cogent link unless the ATT link fails. Another option is sending them the community string to set local preference, but that can get trickier because they don't publish the default local pref of their peers versus their customers. 174:70 is too low, and would cause all routes to take ATT, including Cogent themselves, 174:120 might be something to try. Verify everything with Looking glasses. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, October 24, 2008 4:18 PM To: [EMAIL PROTECTED]; cisco-nsp@puck.nether.net Subject: Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement Arie, Thank you for your response. In my situation, where everything is normal, I am actually sending their specific communities for them not to advertise my route to their peers. My only problem is how to change that automatically when my default route from ATT goes away (ATT circuit does down and I'm in a failover situation)? Thank you, -Original Message- From: Arie Vayner (avayner) [mailto:[EMAIL PROTECTED] Sent: Fri 10/24/2008 6:03 PM To: Kacprzynski, Tomasz; cisco-nsp@puck.nether.net Subject: RE: [c-nsp] BGP Multihomed Selective/Conditional Advertisement Tom, Instead of not advertising a certain prefix, there is another alternative using BGP communities which are recognized by your upstream providers. Take a look for what Cogent supports for example (better ask them for the official list...): http://www.onesc.net/communities/as174/ You could play with the local pref communities or the no-export ones Its not the full answer, but just another idea... Let me know if you are still stuck... Arie -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, October 24, 2008 23:07 PM To: cisco-nsp@puck.nether.net Subject: [c-nsp] BGP Multihomed Selective/Conditional Advertisement I have been trying to figure out how to do this and maybe someone will be able to help me out. I have two ISP connections ISP ATT and ISP Cogent. (ISP Cogent)(ISP ATT) | | RO --- R1 ATT would be used for primarily internet and access to our webservers. Cogent would be primarily used to access Cognet's network that use VPN for incoming connections only. I do not want to have other networks besides Cogent's network using this path to access our webserver. I would like to have each other act as a backup for one another. For instance if ATT fails I want everyone on the internet use Cogent to access me. If Cogent fails I want everyone on the internet and the VPN connections on Cogent's network to use ATT. So basically what I was thinking to setup is to accept a default router from ATT and Cogent. Lower the local preference of Cogent and that way I would accomplish using ATT as primary internet access. The tricky part is with Cogent and using then to only access their local networks. Looking through communities I found out Cogent's communities that would not export my route to their peers and keep it internal within their AS. This works fine but the problem now is how do I failover if ATT fails? How do I automatically change my not-export community I'm sending to Cogent to start adverting the route to its peers? I looked at conditional advertisement, I was able to basically send the route map with not-export communities to Cogent if the default route from ATT is present. The problem with this is that once the default router disappears it doesn't advertise anything to Cogent, none of my routes are advertised to Cogent. I'm not sure if I could do this sort of a double condition such as if ATT's default route is present send out to Cogent a route map with prefixes to not-export my routes if ATT's default route is not present sent to Cogent a route map without any communities on my routes Basically I'm trying to figure out how I can have multihoming, but with the constrains that I want 1
Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement
--- On Sun, 26/10/08, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: From: [EMAIL PROTECTED] [EMAIL PROTECTED] Subject: RE: [c-nsp] BGP Multihomed Selective/Conditional Advertisement To: [EMAIL PROTECTED], cisco-nsp@puck.nether.net Date: Sunday, 26 October, 2008, 3:54 AM I'm not sure if I can have multiple advertise-maps also, but can't find any documentation on it either. Does anyone else know? I tried something similar to what you posted: Yep, I saw an email with a different subject that had pretty much what I said, sorry about that, I started reading this thread and responded to it before I read the other one. neighbor COGENT_NEIGHBOUR_IP advertise-map ADVERTISE_WITH_COMMUNITIES exist-map DEFAULT-ATT-PREFIX neighbor COGENT_NEIGHBOUR_IP advertise-map ADVERTISE_ALL non-exist-map DEFAULT-ATT-PREFIX but I was tracking for the same route-map DEFAULT-ATT-PREFIX on both, not NON_EXIST_ATT_PREFIX and EXIST_ATT_PREFIX. Do you think that could matter? You should be able to track the same prefix for both if it's valid to have an exist and nonexist map for the same neighbour (which I still don't know if that is valid). With the above config it only matched on my first advertise-map and keeps it in withdraw state. The other tip I can give if you try setting something like this up is to NOT track the default route from ATT. Find a prefix that they use on their core network (ie. an ATT subnet that if you weren't seeing it would mean bad things had happened) and track that one. Why do you think a different route be different? The reason I ask is that i'm planning on only getting a default rotue from ATT. When I first tried doing this (but only using nonexist) I couldn't get it to work properly. Link to ISP_A would go down and the router would start advertising subnet to ISP_B then link A would come up a again and sometimes it would fail back, sometimes not. I opened a TAC case and one of the first things the Cisco guys said thou shouldst not track thy default route for exist or nonexist advertisements. You need to track another route that if it ceases to exist means that you link to ATT is cactus. In the scenario when I was doing this, we ended up tracking a /16 that the ISP used on their core national backbone. If that route ceased to exist, then our link to the ISP might still be up, but their network would be screwed big time so we should start advertising to ISP_B. I have no idea what ATT offer as options for routes to send you, but hopefully they'll offer something like default + local. Local routes being ones that are originated from within their ASN only. Once you are getting more than the default route, you just filter out everything except the default your tracking route anyway, like this: === ip prefix-list att-all seq 10 permit 0.0.0.0/0 ip prefix-list att-all seq 20 permit 2.2.0.0/16 ! ! you need to substitute 2.2.0.0/16 for the ATT route you're tracking ! route-map from-att permit 10 match ip address prefix-list att-all ! neighbor ATT_NEIGHBOR_IP route-map from-att in === If you're concerned about bogging your router down, I wouldn't be. I've done this on both a 1751 1861 router where the number of routes received from the ISP when I asked for default + local was over 14,000. It just chucks out all the others and only puts the two (default + tracking route) in the route table. Another thing I tried was neighbor COGENT_NEIGHBOUR_IP advertise-map ADVERTISE_WITH_COMMUNITIES exist-map DEFAULT-ATT-PREFIX neighbor COGENT_NEIGHBOUR_IP route-map ADVERTISE_ALL out So the idea was to advertise the route-map once advertise-map withdraws the ADVERTISE_WITH_COMMUNITIES. Coudn't get that to work either. Does anyone know where advertise-map fits with the order of exporting routes? I have no idea and I can't find any good doco on using advertise maps with tracking maps. All I can find is command reference stuff, which doesn't give any real idea on how you can/can't use the stuff. ___ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement
You can use EEM to run commands on other routers, it's not the best at doing remote telnet/ssh but it can do it to some extent, its the interactive stuff that seemed to really kill it last time I tried but a simple command would work, it may be better for that now. So essentially you would create your app on R1 based on the event of BGP peer going down, then the action would be to open a session to R0 and change that route-map for your communities and execute a clear ip bgp x.x.x.x out, whether you can do all of that via EEM remotely i'm not sure, on the same router would be no problem. You could just write an expect script if you have a unix host somewhere there for management and have the EEM trigger that if it's easier, I could even write you the expect script if you want, it's pretty simple. Ben -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Sunday, 26 October 2008 3:25 AM To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; cisco-nsp@puck.nether.net Subject: RE: [c-nsp] BGP Multihomed Selective/Conditional Advertisement In this particular setup the router R0 wouldn't be peering with ATT's router, it would get the default router from R1 with is my other router, so I would not get the neighbor down alert. (ISP Cogent)(ISP ATT) | | RO --- R1 Is there a way to use event manager to track a default route with communities set on it or defaul route with next hop to monitor as an event and take action based on that? Thank you, From: Ben Steele [mailto:[EMAIL PROTECTED] Sent: Fri 10/24/2008 8:55 PM To: 'Ben Steele'; Kacprzynski, Tomasz; [EMAIL PROTECTED]; cisco-nsp@puck.nether.net Subject: RE: [c-nsp] BGP Multihomed Selective/Conditional Advertisement Ah my apologies I should have read your original email, your problem is a little more trickier than that. After having read your original one though I believe you could probably do this with an event manager task used to watch logging for bgp neighbour failure you could trigger it to modify your export community and do a clear ip bgp x.x.x.x out Ben -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ben Steele Sent: Saturday, 25 October 2008 10:44 AM To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; cisco-nsp@puck.nether.net Subject: Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement If it's purely just for failover (ie you don't want to get billed for traffic down your failover link while your active is up) then why not just send the community: 174:70 70 Set customer route local preference to 70 This will make them use ATT's path until the ATT link goes down. Ben -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Saturday, 25 October 2008 9:48 AM To: [EMAIL PROTECTED]; cisco-nsp@puck.nether.net Subject: Re: [c-nsp] BGP Multihomed Selective/Conditional Advertisement Arie, Thank you for your response. In my situation, where everything is normal, I am actually sending their specific communities for them not to advertise my route to their peers. My only problem is how to change that automatically when my default route from ATT goes away (ATT circuit does down and I'm in a failover situation)? Thank you, -Original Message- From: Arie Vayner (avayner) [mailto:[EMAIL PROTECTED] Sent: Fri 10/24/2008 6:03 PM To: Kacprzynski, Tomasz; cisco-nsp@puck.nether.net Subject: RE: [c-nsp] BGP Multihomed Selective/Conditional Advertisement Tom, Instead of not advertising a certain prefix, there is another alternative using BGP communities which are recognized by your upstream providers. Take a look for what Cogent supports for example (better ask them for the official list...): http://www.onesc.net/communities/as174/ You could play with the local pref communities or the no-export ones Its not the full answer, but just another idea... Let me know if you are still stuck... Arie -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, October 24, 2008 23:07 PM To: cisco-nsp@puck.nether.net Subject: [c-nsp] BGP Multihomed Selective/Conditional Advertisement I have been trying to figure out how to do this and maybe someone will be able to help me out. I have two ISP connections ISP ATT and ISP Cogent. (ISP Cogent)(ISP ATT) | | RO --- R1 ATT would be used for primarily internet and access to our webservers. Cogent would be primarily used to access Cognet's network that use VPN for incoming connections only. I do not want to have other networks besides Cogent's network using this path to access our webserver. I would like to have each other act as a backup for one another. For instance if ATT fails I want everyone on the internet use Cogent to access me. If Cogent fails I want everyone on the internet and
[c-nsp] ospf network type
Suppose you have 2 routers dual-uplinked in a 'V' to 2 more routers using point-to-point (/30) links over ethernet. There are four separate /30 segments. Since these are broadcast segments, a DR/BDR will be elected on each link. In this type of topology, does it make more sense to just make the network type point-to-point? What are the advantages of changing the network type -- fast convergence? Thanks for helping me understand the difference. /b ___ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
Re: [c-nsp] ospf network type
On Sunday 26 October 2008 09:52:33 Brian Spade wrote: What are the advantages of changing the network type -- fast convergence? This topic was discussed quite a bit on this list. Here's the thread from the archives: http://puck.nether.net/pipermail/cisco-nsp/2008-August/053445.html Cheers, Mark. signature.asc Description: This is a digitally signed message part. ___ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
Re: [c-nsp] ospf network type
Thanks Mark, that thread was very useful and answered my questions. My question stemmed from an insight into the best practice for this type of topology. Putting aside having to add additional commands for your OSPF configuration, the only advantage I see of changing the network type from broadcast to point-to-point is quicker OSPF adjacencies. So all-in-all, it probably doesn't make too much of a difference changing the default network type for this topology. /b On Sat, Oct 25, 2008 at 7:51 PM, Mark Tinka [EMAIL PROTECTED]wrote: On Sunday 26 October 2008 09:52:33 Brian Spade wrote: What are the advantages of changing the network type -- fast convergence? This topic was discussed quite a bit on this list. Here's the thread from the archives: http://puck.nether.net/pipermail/cisco-nsp/2008-August/053445.html Cheers, Mark. ___ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
