Re: [c-nsp] cisco interface shutdown detection, how is possible?
On 07-Jan-13 8:32 AM, h bagade wrote: I've also tested Cisco router connection on different systems with different OSes. On Win systems, when I disable the Ethernet card, router detects it at the time but on FreeBSD systems, when I set interface down, the router shows Line Protocol as up! Blame the driver on the FreeBSD. Many modern unix-like system do not bother to implement interface shutdown in the driver or if they do they do not call that function when you do an ifconfig interface down. Dumitru ___ 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] cisco interface shutdown detection, how is possible?
On 01/07/2013 06:32 AM, h bagade wrote: Can I conclude from all discussions above that the ethernet protocol support a feature named dying gasp which inform the other end that it is going to shutdown? It seems that it works when we intentionally try to shutdown an interface but when there is a failure on layer2 connection it couldn't help?! No. The spec contains this feature, but virtually nothing supports it. Link detection on ethernet is actually a slightly subtle area, but if: 1. You have autoneg enabled, and 2. The devices are *DIRECTLY* connected ...you can be sure it will work IF THE LINK GOES DOWN. There's a lot of confusion in your emails, but what I think you're asking is: if you connect two Cisco devices, how is one able to detect the other doing shutdown? ...the answer is that on a Cisco, shutdown actually disables the physical layer, and the other Cisco detects this. In your case, the other device (BSD) is not doing this, so this doesn't happen. There's no magic - if the light/electricity goes away, the Cisco will see line down. If it doesn't, it won't. ___ 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] cisco interface shutdown detection, how is possible?
h bagade baga...@gmail.com writes: I've also tested Cisco router connection on different systems with different OSes. On Win systems, when I disable the Ethernet card, router detects it at the time but on FreeBSD systems, when I set interface down, the router shows Line Protocol as up! Be careful to not be fooled by IPMI either. If IPMI is configured, the link may stay up even though the OS believes it is down. Indeed, the link may stay up even though the server is off (though of course it dies if the server loses power). Some servers are shipped factory-default with IPMI enabled on the regular ethernet interfaces. /Benny ___ 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] cisco interface shutdown detection, how is possible?
Can I conclude from all discussions above that the ethernet protocol support a feature named dying gasp which inform the other end that it is going to shutdown? It seems that it works when we intentionally try to shutdown an interface but when there is a failure on layer2 connection it couldn't help?! I've also tested Cisco router connection on different systems with different OSes. On Win systems, when I disable the Ethernet card, router detects it at the time but on FreeBSD systems, when I set interface down, the router shows Line Protocol as up! I tried to capture packets with Wireshark on Win system to find out if any packet is sent out before the interface is disabled but I see no packet! I thought maybe it stops capturing on interface and then send the supposed packet out! I really confused by what I saw in different scenarios! I need help to fix it up. On Sat, Jan 5, 2013 at 11:15 PM, Jay Hennigan j...@west.net wrote: On 1/5/13 3:44 AM, h bagade wrote: Hi all, I was wondering how Cisco routers could detect the directly connected interface at the other end is shutdown! there are two general possibility on my point of view: 1- the other device is sending special information before shutting down the interface. 2- there are some method of polling which is done periodically and based on the answer, the router detect the interface is up or no! Some of this depends on the layer 2 protocol (Ethernet vs. DS-3 for example) but in most cases there isn't any detectable difference between the remote end being administratively shut down and a failure of the interconnecting medium. The exception is that in some metro ethernet scenarios you can use OAM to capture dying-gasp, error disable, or shutdown events. It isn't a periodic poll, but rather like a one-time Going down now!, your scenario 1. As Cisco router is not able to detect the interface shutdown on the other side when connected to some other device, not Cisco like unix systems, it seems, it has some sort of protocol for detection which is number 2 of above guesses! The router will absolutely detect the lack of line protocol and carrier and flag the link as down but this would be the case whether the remote side is administratively shut down or the cable is just unplugged. could you please help me on this? Or provide me a scenario witch I could find out if any packet is transmitted between Cisco routers to inform the interface shutdown! See: http://www.cisco.com/en/US/docs/switches/metro/me3400/software/release/12.2_46_se/configuration/guide/swoam.pdf -- Jay Hennigan - CCIE #7880 - Network Engineering - j...@impulse.net Impulse Internet Service - http://www.impulse.net/ Your local telephone and internet company - 805 884-6323 - WB6RDV ___ 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] cisco interface shutdown detection, how is possible?
Hi, I was wondering how Cisco routers could detect the directly connected interface at the other end is shutdown! there are two general possibility on my point of view: 1- the other device is sending special information before shutting down the interface. 2- there are some method of polling which is done periodically and based on the answer, the router detect the interface is up or no! Neither. The router just sees the power or light disappear on the interface... Sander ___ 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] cisco interface shutdown detection, how is possible?
On (2013-01-05 15:14 +0330), h bagade wrote: I was wondering how Cisco routers could detect the directly connected interface at the other end is shutdown! If it is truly directly connected, it should go down in both ends at RTT/2 delay. Maybe you've disabled autonegotiation which may break this? Interestingly enough, ethernet standard allows autonegotiation to send type of 'dying gasp' when operationally shutdown. I.e. far-end device could differentiate link-loss due to link-cut/HW issue and link-loss due to intentional shutdown of remote end. Someone I know checked specs of particular common broadcom chip and this feature is supported in HW. For some reason router vendors are not supporting it in software. I personally would love to see in syslog special line if we detected linkdown due to remote end shutdown. -- ++ytti ___ 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] cisco interface shutdown detection, how is possible?
On 1/5/13 3:44 AM, h bagade wrote: Hi all, I was wondering how Cisco routers could detect the directly connected interface at the other end is shutdown! there are two general possibility on my point of view: 1- the other device is sending special information before shutting down the interface. 2- there are some method of polling which is done periodically and based on the answer, the router detect the interface is up or no! Some of this depends on the layer 2 protocol (Ethernet vs. DS-3 for example) but in most cases there isn't any detectable difference between the remote end being administratively shut down and a failure of the interconnecting medium. The exception is that in some metro ethernet scenarios you can use OAM to capture dying-gasp, error disable, or shutdown events. It isn't a periodic poll, but rather like a one-time Going down now!, your scenario 1. As Cisco router is not able to detect the interface shutdown on the other side when connected to some other device, not Cisco like unix systems, it seems, it has some sort of protocol for detection which is number 2 of above guesses! The router will absolutely detect the lack of line protocol and carrier and flag the link as down but this would be the case whether the remote side is administratively shut down or the cable is just unplugged. could you please help me on this? Or provide me a scenario witch I could find out if any packet is transmitted between Cisco routers to inform the interface shutdown! See: http://www.cisco.com/en/US/docs/switches/metro/me3400/software/release/12.2_46_se/configuration/guide/swoam.pdf -- Jay Hennigan - CCIE #7880 - Network Engineering - j...@impulse.net Impulse Internet Service - http://www.impulse.net/ Your local telephone and internet company - 805 884-6323 - WB6RDV ___ 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/
