VLANs thru several switches to router on a stick 1

[netadmin65]

I am doing inter-VLAN routing, etc. from a Cisco 4506
with SUP2 (CatOS) to a 2621XM router.

I am performing "router on a stick" (one actual physical
interface, many logical sub-interfaces) using dot1q
tagging.

I have the sub-ints set up on the router correctly.
Since I am using DHCP for the PCs on the VLAN, I have
each sub-int set up with an IP address and a helper address,
the correct encapsulation (dot1q) and any ACLs I may need
to use.

I then have the port from the switch to the router set up
as a trunk port on the switch. For each port on the Cisco
4506, I have them members of their respective VLANs, and
this configuration works perfectly.

However, I also have 4 Cisco 3550 switches with extended
image connecting with GBICs to GBICs on the 4506. When I
attempt to have VLANs that are created on these switches,
try to get recognized via their dot1q tags by the router,
I cannot get this to work, and in addition, it appears
that this somehow stops the switch eventually from
performing correctly. It is only when I remove the specific
sub-int on the router, that conforms to a VLAN on one of the
3550 switches, that I can again operate the switch.

In short, the VLANs on the 4506 direct to the router
work flawlessly. The VLANs on the 3550 switches, going
through the 4506 to get to the router do not work.

I have tried several things, usually involving trunking
the GBICs also.

Important: I will not upgrade the 4506 to SUP3 or SUP4,
because of price, and also due to the fact that it does not
seem to be the problem here.

Any expert advice is welcome.... Thanks

 

[netadmin65]

Hi! netadmin65 again.

I think I found the answer in:

http://www.tek-tips.com/viewthread.cfm?SQID=728613&SPID=558&page=7

However, several questions.....

Do I need to set up the GBICs on BOTH SIDES (both 3550
end and 4506 end) as trunk ports?

Also, do I need to set up the vlan database on BOTH
switches?

Please help....

 

[bierhunter]

The router on a stick should work fine as you are expecting it to.

Here are some things to check:

1. Router to 4506 = 802.1Q trunk (sounds like you got that one)

2. VLAN-1 for management, other VLANs for hosts.

3. 4506 to other switches should be 802.1Q trunks assigned to VLAN-1.

4. 4506 should be VTP Server, other switches, VTP clients.

5. All in the same VTP domain.

6. The switchports for the hosts will need to be assigned to their respective VLANs. Keep VLAN-1 only for management. The Trunk links will use VLAN-1.

Something I've had to do in the past with router on a stick is to manually assign the ports on the directly connected switch (4506 here) to each of the vlans in order for them to show up in the vlan table. Then they got propogated to the other switches. Once that happens, you can then reset the ports to the vlan they need.

Hope that helps. If I've forgotten something, I'm sure someone will help out.

 

[BuckWeet]

Well one thing, if you have 3550's coming, then don't use the 2620XM as your router.. I'm not sure how much actual intervlan traffic you'll have, but the 3550's even if they aren't the core switch will still give you much higher performance than the router will..


Also one thing to consider is taht you're not wanting to spend the money on a sup3 or sup4, what about a Sup2E? they are layer 3 integrated, but they just can't do some of the advanced features like higher end routing protocols, etc..


BuckWeet

 

[netadmin65]

Wow.... answers so fast. Thanks.... Is SUP2E a different
module, or just an upgraded image? And I'm sure I need
to set both ends of a trunk as trunk ports, but not
wanting to mess things up, I'm still going to ask the
obvious.

As stated before:

Do I need to set up the GBICs on BOTH SIDES (both 3550
end and 4506 end) as trunk ports?

Anyhow, good with routers and PIX firewalls, and IOS
firewall and IDS, as well as the different management
software, just not so hot on switches, and expected
to be the Net Admin, phone switch admin (I do Avaya),
Help Desk, PC Tech, Network Engineer, Web Admin, etc.
the list goes on. I'm sure some of you know what that's
all about.

Thanks again...

 

[bierhunter]

Yes, both sides of the trunk link need to be set up as trunks.