Multi-homed 3550 for Internet Connectivity

Answered Question
Feb 9th, 2007

We have what seems to be a standard campus 6509 layout here.

Our buildings are connected to the Distribution 6509's and each dist 6509 is connected to both of the core 6509's

Our Internet is connected to 7206VXR and connects to the campus through a 3550 which is the source of our static routes.

That 3550 is connected to the campus LAN through a core 6509

I will attach the relevant configs and a badly drawn diagram. :)

My plan is to link that 3550 to the other core 6509 ("C" shown with tiny red line)for redundancy. We had to do some maintenance on the "A" core 6509 and took out the Internet.

I would like for that not to happen.

I was hoping that the forum could make some suggestions of ways to implement this easily.

Scott

I have this problem too.
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Correct Answer by Collin Clark about 9 years 7 months ago

The cloud in your diagram is awesome! What I would do is add the "red" connection to C Core like you mentioned. I would make the links between the 3550 and the two cores L3 links. That way EIGRP will see two equal routes and should load balance across them (assuming you share the load across your cores).

HTH and please rate

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Correct Answer
Collin Clark Fri, 02/09/2007 - 13:03

The cloud in your diagram is awesome! What I would do is add the "red" connection to C Core like you mentioned. I would make the links between the 3550 and the two cores L3 links. That way EIGRP will see two equal routes and should load balance across them (assuming you share the load across your cores).

HTH and please rate

scottbob09 Fri, 02/09/2007 - 13:10

Super, my thoughts exactly.

Where I am now hung up is do I make a new vlans and interfaces on the 3550 and the "C core" 6509? I seem to have a bad feeling about adding the 126 vlan to the "C" core and just assigning an IP in that address space.

scottbob09 Fri, 02/09/2007 - 15:43

I know why this confused me so much. And it still does. I have never setup a routed gig port on a 6509 that runs in hybrid mode. How do I get the IOS side to see the gig port so I can make it a routed port, rather than presenting a vlan to it on the layber 2 side (catos).

Collin Clark Sun, 02/11/2007 - 14:48

Under the interface, enter "no switchport", then configure like a router port.

glen.grant Sun, 02/11/2007 - 15:53

In hybrid mode you cannot do this . You will need to create the layer 3 SVI on the msfc side and then just put the layer 2 port on the supervisor side you want to use into that vlan . It is the same thing as a routed port in Native mode just a different way of doing it . The vlan number can be any number you want to use as long as it is unique on the box. PS hows things in Cortland i'm up in Rochester ....

interface vlan 900

ip adresss x.x.x.x

no shut

layer 2 side

set vlan 900 slot/port

scottbob09 Sun, 02/11/2007 - 16:20

Cortland is good, not much snow...

I wish I could go native IOS on this box, but I have a WS-X6608-T1 in it and it isnt supported in IOS.

So I am going through the hassle of getting catos to a point where I can use the ata flash drive and then throw a new version of IOS on it and hope for the best.

ragarwal123 Sun, 02/11/2007 - 16:59

I have a question to you Scott, What is the purpose of not to configuring the HSRP between "core switch A" and "core switch C".

Have you made diffrent vlans on each core switches and redundancy is happning via EIGRP?

scottbob09 Sun, 02/11/2007 - 18:13

well,

Good question. When I was new to the position this network was just being built. Out implimentor built this network this way. HSRP is only running on the 3550's in our switch rooms that connect some 2950's to VG248's. The 2 cores were never/have never been connected. But to answer your question, I believe there are different VLANS on each core and EIGRP is running.

Maybe it has something to do with the way they had to get appletalk running (which we dont use anymore)

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