OK, this is what I have configured (omitting the obvious and irrelevant):
RTR1#
router bgp 100
neighbor RTR2 remote-as 100
neighbor x.x.x.x peer-group RTR2
neighbor RTR2 send-community
neighbor RTR2 route-map RTR2-OUT out
!
route-map RTR2-OUT permit 10
match ip address prefix-list COMMUNITY-1
set community 100:1
!
route-map RTR2-OUT permit 20
match ip address prefix-list COMMUNITY-2
set community 100:2
!
ip prefix-list COMMUNITY-1 seq 5 permit 1.1.1.0/24
ip prefix-list COMMUNITY-2 seq 5 permit 2.2.2.0/24
RTR2#
router bgp 100
neighbor RTR1 remote-as 100
neighbor y.y.y.y peer-group RTR1
neighbor RTR1 route-map RTR1-IN in
neighbor ISP1 remote-as 11111
neighbor z.z.z.z peer-group ISP1
neighbor ISP1 send-community
neighbor ISP1 route-map ISP1-OUT out
(similar settings for ISP2, with opposite prepending settings)
ip bgp-community new-format
ip community-list standard COMMUNITY-1 permit 100:1
ip community-list standard COMMUNITY-2 permit 100:2
!
route-map RTR1-IN permit 10
match community 100:1
!
route-map RTR1-IN permit 20
match community 100:2
!
route-map ISP1-OUT permit 10
match community COMMUNITY-1
!
route-map ISP1-OUT permit 20
match community COMMUNITY-2
set as-path prepend 100 100 100 100
!
route-map ISP2-OUT permit 10
match community COMMUNITY-2
!
route-map ISP2-OUT permit 20
match community COMMUNITY-1
set as-path prepend 100 100 100 100
!
Now, checking what I see, I get the following:
RTR1# sh ip bgp neighbor x.x.x.x advertised
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.0/24 0.0.0.0 0 32768 i
*> 2.2.2.0/24 0.0.0.0 0 32768 i
RTR2# sh ip bgp neighbor y.y.y.y received-routes
Network Next Hop Metric LocPrf Weight Path
* i1.1.1.0/24 207.226.45.254 0 100 0 i
* i2.2.2.0/24 207.226.45.254 0 100 0 i
RTR2# sh ip bgp 1.1.1.0
BGP routing table entry for 1.1.1.0/24, version 7234660
Paths: (1 available, no best path)
Not advertised to any peer
Local, (Received from a RR-client), (received-only)
y.y.y.y (metric 100) from y.y.y.y (y.y.y.x)
Origin IGP, metric 0, localpref 100, valid, internal
Community: 100:1
Same result for 2.2.2.0/24, as you can see, community is seen correctly, now,
if seen, then it must be matched and set to go out to ISPs, theoretically,
however:
RTR2# sh ip bgp neighbor z.z.z.z advertised
Total number of prefixes 0
BUMMER!!!!
What I do find very strange is the following:
route-map RTR1-IN, permit, sequence 10
Match clauses:
community (community-list filter): 100:1
Set clauses:
Policy routing matches: 0 packets, 0 bytes
route-map RTR1-IN, permit, sequence 20
Match clauses:
community (community-list filter): 100:2
Set clauses:
Policy routing matches: 0 packets, 0 bytes
route-map ISP1-OUT, permit, sequence 10
Match clauses:
community (community-list filter): COMMUNITY-1
Set clauses:
Policy routing matches: 0 packets, 0 bytes
route-map ISP1-OUT, permit, sequence 20
Match clauses:
community (community-list filter): COMMUNITY-2
Set clauses:
as-path prepend 100 100 100 100
Policy routing matches: 0 packets, 0 bytes
See? all the counters are zero!
I tried resetting all the sessions in and out, soft, hard, harder, nothing!
I'm sure I'm missing something here!
Please help
Ziv
-----Original Message-----
From: Andriy Bilous [mailto:[email protected]]
Sent: Wednesday, August 03, 2011 5:44 PM
To: Ziv Leyes
Cc: [email protected]
Subject: Re: [c-nsp] Dumb question
Yup, match community accepts community-list as an argument, not the
'raw' value. So you need first define them
ip community-list 1 permit xx:1
ip community-list 2 permit xx:2
The whole config should be like that
RTR1
router bgp 100
nei RTR2 remote-as 100
nei RTR2 send-community
nei RTR2 route-map SET_COMM out
route-map SET_COMM permit 10
match ip addr pref COMM_XX1
set community xx:1
route-map SET_COMM permit 20
match ip addr pref COMM_XX2
set community xx:2
route-map SET_COMM permit 30
ip prefix-list COMM_XX1 permit 1.1.1.0/24 le 32
ip prefix-list COMM_XX2 permit 2.2.2.0/24 le 32
RTR2
router bgp 100
nei RTR1 remote-as 100
nei RTR1 send-community
nei ISP1 remote-as ISP1
nei ISP1 route-map ISP1_OUT out
nei ISP2 remote-as ISP2
nei ISP2 route-map ISP2_OUT out
route-map ISP1_OUT permit 10
match community ISP1
set as-path prepend 100 100 100
set community none
route-map ISP1_OUT permit 20
route-map ISP2_OUT permit 10
match community ISP2
set as-path prepend 100 100 100
set community none
route-map ISP2_OUT permit 20
ip community-list ISP1 permit xx:2
ip community-list ISP2 permit xx:1
And you need to reset the BGP sessions to both peers to propagate
changed information
clear ip bgp ISP[1-2] soft out
On Wed, Aug 3, 2011 at 3:19 PM, Ziv Leyes <[email protected]> wrote:
> Well, I tried to simplify the scenario to only concentrate on my problem, the
> scenario is a little bit more complicated, but not relevant for the question
>
> The question is, given the fact I'm trying to manage the eBGP advertising
> decisions based on what is happening on RTR1.
> Let's suppose I need to give operators access only to RTR1 but I want them to
> decide which prefixes will be advertised to which ISP, but they can't get
> access to RTR2 to do it there, so I want to setup RTR2 to do the advertising
> matching the decisions that were made on RTR1.
>
> I just spoke with a friend and he told me that maybe I need to rewrite the
> communities, for example RTR1 advertises prefix 1.1.1.1/24 with community
> xx:1 and 2.2.2.2/24 with xx:2
> RTR2 has an incoming route-map towards RTR1 that allows filters routes
> according to matching communities.
> Now I have two prefixes that are seen with their communities, what I simply
> tried to do was a route-map outgoing towards the ISPs that match the
> community (that came from the RTR1) and then advertise them over the ISPs
> with or without prepending, according to my previously chosen decision.
> My friend thinks I need to match the community on the route-map in from RTR1
> and then set a new community, e.g
>
> route-map RTR1-IN permit 10
> match community xx:1
> set community yy:1
> route-map RTR1-IN permit 20
> match community xx:2
> set community yy:2
> !
> route-map ISP1 permit 10
> match community yy:1
> route-map ISP1 permit 20
> match community yy:2
> set as-path prepend ........
>
> and viceversa for ISP2
>
> What I tried was matching community xx:1 and xx:2 as they came from RTR1,
> perhaps here's the problem?
>
> Ziv
>
>
> -----Original Message-----
> From: Harold 'Buz' Dale [mailto:[email protected]]
> Sent: Wednesday, August 03, 2011 4:00 PM
> To: Ziv Leyes; [email protected]
> Subject: RE: Dumb question
>
> It seems to me that RTR 2 is the one advertising the routes to ISP1 and ISP2
> and the path from RTR2 to both of these nets is RTR1 via the same link. Would
> be much easier to do this from RTR2.
>
> Buz
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Ziv Leyes
> Sent: Wednesday, August 03, 2011 8:54 AM
> To: [email protected]
> Subject: [c-nsp] Dumb question
>
> Hi all,
> I have the following scenario (excuse my lousy ascii art...)
>
>
>
> ISP1
> /
> /
> /
> RTR1 -----iBGP----- RTR2
> \
> \
> \
> ISP2
>
> For the simplicity of the case, I have two prefixes, 1.1.1.1/24 and
> 2.2.2.2/24,
> I want to advertise prefix 1.1.1.1/24 to ISP1 as best, and 2.2.2.2/24 to ISP1
> with prepends, and the opposite too, prefix 2.2.2.2/24 to ISP2 as best and
> prefix 1.1.1.1/24 to ISP1 with prepends.
>
> What I'm trying to do is to set up all in a way that the only place I set up
> my decision is on RTR1 only, and that will be reflected via the iBGP to RTR2
> about how I want the prefixes to be advertised to my eBGP neighbors ISP1 and
> ISP2
> I tried setting communities, but all I got is RTR2 to see and match the
> communities, but based on this, I couldn't get the prefixes advertised to the
> ISPs at all.
>
> What kind of manipulation I need to do in order for the RTR2 after matching
> the communities coming from RTR1, to advertise it to the ISPs according to
> the priorities I've mentioned before?
>
> This sounds very basic and not so complicated to do, but I guess I'm missing
> something here!
>
> Please help, and if possible, don't send me links to cisco web site case
> studies or to some 300 pages PDF about how BGP and communities work. A simple
> straight forward example of how this can be set will be enough.
> Thanks!
> Ziv
>
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