Cisco High availavility tracking

Hi all,

I have repeatedly been told by my teachers that the interfaces I should track (assuming a cisco campus topology with core and distribution layers, with intervlan routing placed on distribution) when using either HSRP or GLBP are the ones that go up to core layer. I don´t completely argue with that, but:

As hosts on the same vlan should be in the same switch, wouldn´t it be more important to track the layer 2 link that connects distribution with access?

And question B: Is there any scenario where distribution multilayer switches are connected by a layer 2 link?

I love reading, especially interesting things, so please don´t be afraid to elaborate.

Thanks in advance.

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Comments

networker050184

ICMP redirect is not dealing with L2 paths.

I still see no benefit whatsoever to track the access link. Added complexity only.

EdTheLad

_Gonzalo_ wrote: »

I might be misunderstanding this sentence, but I thought that the path ICMP redirect looked was the L2 path to gateway, not L3 from gateway. After all, routing will already take care of that path, wouldn´t it?

ICMP redirect looks at an incoming packets destination ip address and examines the RIB, if it see's that the packet src address is in the same subnet as the best routes next-hop, and it sends a redirect to the host to tell it to go directly to the other gateway on the same lan segment.

Perfect world scenario was in regards to having all vlans on the one switch not dispersed throughout the L2 network. Configuring 2 HSRP groups per subnet as a workaround to make your L2 network more dynamic in regards to the L3 network has no impact on the perfect world.

Yes, your patch would work in the perfect world, but my patch will work in our world

_Gonzalo_

networker050184 wrote: »

ICMP redirect is not dealing with L2 paths.

Cr*p! So, if it does not deal with L2, that previous post of mine is worth nothing...

networker050184 wrote: »

I still see no benefit whatsoever to track the access link. Added complexity only.

I know, and I actually agree with what you first posted. But as this post has had +400 views and not so many participants, I assume that people are reading and not posting, so I wanted to clarify for them as well.

So, if that´s the case, I guess that ICMP redirect would only be of use when D1-D2 link is L2 AND it would be like using tracks to core.

Well, I still count this as valuable knowledge, and so as a victory. Even if what I wanted to do would never be possible in real life, I learned a lot about tracks, I was impressively introduced to ICMP redirects and understood the different ways and hows regarding Distribution layer connections.

_Gonzalo_

EdTheLad wrote: »

Yes, your patch would work in the perfect world, but my patch will work in our world .

Hahaha

_Gonzalo_

Thanks again guys. It´s really good to have people to think with! And even more if they know a cr*pload more than me!!

_Gonzalo_

For those who have been reading this but are starting with HSRP (initial config, priority, tracks, preempt) I have found a great video tutorial at cisco, while looking for more info on this thread´s content (remember that you need a cisco.com ID to watch it):

https://learningnetwork.cisco.com/docs/DOC-4309

I kind of liked it. You are also requested to answer a few questions about HSRP config/behaviour.