Questions on Multi-Layer Switching Architecture

[haithamnofal]

Hi,

I have multi-layer architecture of Access, Distribution, and Core Layer switches making up the HQ site; I am running EIGRP routing protocol in this network, I also have a 4500 switch connected to the distribution layer which is connecting the WAN module to the HQ site. The 4500 switch is running both EIGRP process which is used in the HQ site and is also the border of an OSPF process used in the remote sites. I am redistributing EIGRP into OSPF and static routes into EIGRP.

I would like to check on the following:

1. Do I also need to redistribute OSPF into EIGRP as I am redistributing EIGRP into OSPF?

2. Do I need to configure any default static routes on any of the switches layers or will the dynamic routing take care of the default route as it is taking care of the specific routes?

3. In the Access layer switch I know I will need to configure the ?IP helper-address? to relay DHCP broadcasts from the users to the DHCP server which is connected to the core switch; do I also need to configure the same on the Distribution and Core switches? If so, I am having L3 connectivity between the Access and the Distribution switches so on which interfaces on the distribution and core switches I should configure this command?

4. Does the L3 link I have between the Access and the Distribution layer pass VTP and STP L2 protocols information?

Thanks,

Haitham

[Jon Marshall]

Haitham

1) It depends on what devices need to see what routes. Can you connect from your HQ to the remote sites already. Is that what the statics are for ?

2) Again it comes back to what your routing requirements are. Do you need a default route or are all your networks reachable as is.

3) No you should not need ip helper-address on the distribution or core. You only need an ip helper-address on vlans with directly attached clients.

4) No the layer 3 link will not pass VTP and STP information. If you are using L3 from your access layer to your distribution then layer 2 is confined to the access-layer.

HTH

[haithamnofal]

Hi Jon,

The users will need to talk with the remote sites which are running OSPF; the HQ is running EIGRP. When redistributing EIGRP into OSPF the remote sites will know how to route to the HQ but won't I need to redistribute OSPF into EIGRP in order for the HQ to learn the routes to the remote sites?

Thanks,

Haitham

[Jon Marshall]

Hi Haitham

Yes you will need to distribute OSPF into EIGRP at the HQ site for routing back to the remote sites.

When doing mutual redistribution ie OPSF into EIGRP, EIGRP into OSPF you need to be careful you don't create routing loops.

HTH

[Jon Marshall]

Hi Haitham

Yes you will need to distribute OSPF into EIGRP at the HQ site for routing back to the remote sites.

When doing mutual redistribution ie OPSF into EIGRP, EIGRP into OSPF you need to be careful you don't create routing loops.

HTH

[Jon Marshall]

Haitham

Attached is a link to redistribution and routing protocols. Have a look at the "Avoiding problems due to redistribution".

HTH

[haithamnofal]

Probably you forgot to paste the link talking about routing loops; please send it again.

Thanks,

Haitham

[Jon Marshall]

Sorry Haitham

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009487e.shtml#avoidredist