HRSP setup

[Horacio Gutierrez]

Let say I have one router connected to two distribution switches called and A and B and obviously there is are trunk between them and they both running  HSRP and distribution A switch is the passive and B active, then the access switch 1 is connected to both distribution switch A and B.  Let say the port that access switch is connected to distribution B as well as all the physical trunks between the two distribution switches goes down completetly can the distribution switch A foward packets from the access swithch to the router.  At this point there is only connectivity from the distribution switch A to the  access switch.

[Jon Marshall · Accepted solution]

Yes it can forward packets but as with your other questions you are still overlooking the fact that both switches would become active if the trunk link goes down.

So it is not really relevant whether there is a traffic path from the access switch to the router. If both switches become active you need to sort that out because it will create problems in your network.

If the trunk between your distro switches fails completely then that is a major network failure and the least of your worries is whether you have a path from the access switch to the router.

Jon

[Horacio Gutierrez]

But if we were using VSS that problem about the trunk being down between the distro switches would not be a a problem

because both switches would be active I am wrong or right?

[Jon Marshall]

VSS uses a link called a VSL link between the 2 switches. If this went down then both switches become active, not just HSRP, but active for all protocols they are responsible for. This would be even more disruptive than both switches becoming HSRP active.

The key thing to understand is that HSRP and VSS are actually quite different things.

HSRP is concerned only with providing a redundant gateway to end devices ie. you make the default-gateway of the clients the virtual IP (VIP) and then one of the switches assumes responsibility for that VIP. If the switch fails then the other switch assumes responsibility for it and the clients can still forward packets. But that is all HSRP is responsible for, nothing else.

VSS on the other hand is make 2 6500 switches into one logical switch. It is concerned with far more than simply redundancy for end clients. It provides not only that but allows for centralised management of the 2 switches and is seen by other devices on the network as one switch which has advantages in terms of STP (Spanning Tree Protocol) etc.

So they are not really comparable or rather VSS does eliminate the need for HSRP but it does a lot more than that and you wouldn't choose a VSS system over other switches simply based on whether you want to run HSRP or not.

Jon

[Horacio Gutierrez]

So this image above show a difference between a non vss network to vss network.  From what I understand the non vss on the left only one link on each access switch has connectivity and the other link from the access switch is on standy which is used to avoid a spanning tree loop and the right image both links from the access switch are being used which speeds data fowarding, I'm I correct or not Jon?

[Jon Marshall]

Yes you partially correct. In the traditional model assuming that the distro switches are connected via a L2 trunk one of the uplinks from the access switch is blocked by STP. It is important to note that this is done on per vlan basis so if you had 2 vlans on the access switch you could have one vlan forwarding on one link and the other vlan forwarding on the other link. But yes for each vlan one of the uplinks will be blocked. Note this nothing to do with HSRP, this is to do with STP.

With the VSS setup both links will be forwarding because the 2 6500 switches running VSS are seen as one logical switch by STP so neither link is blocked. Again this is nothing to do with HSRP but STP.

Jon