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Intervlan routing - small network

George B. Park, III
Occasional Contributor

Intervlan routing - small network

Quick question.

Using three 5400 switches I have (5) VLANs across them.

Each VLAN has an IP address that is part of the network making up that vlan (and part of a /22 overall allocation):

VLAN 20 -
10.10.20.10 Switch 1 VLAN 20
10.10.20.11 Switch 2 VLAN 20
10.10.20.12 Switch 3 VLAN 20
VLAN 21 -
10.10.21.10 Switch 1 VLAN 21
10.10.21.11 Switch 2 VLAN 21
10.10.21.12 Switch 3 VLAN 21
VLAN 22 -
10.10.22.10 Switch 1 VLAN 22
10.10.22.11 Switch 2 VLAN 22
10.10.22.12 Switch 3 VLAN 22

One of the 5400s will be the core, the others closets.

I've set up LACP trunks between all switches with all VLANs tagged across them.

Right now I have untagged hosts in VLAN 21 which are unable to ping hosts in VLAN 20 but can ping members of either VLAN no matter what switch they are on.

That is a problem since hosts in VLAN 21 (users) should be able to get to hosts in VLAN 20 (servers).

The switches can ping either of the hosts on either VLAN without issue, every time.

Having a small network address allocation I wanted to make sure that this was the correct way of setting the switches up before enabling RIP on them to manage routing (no trunking to an upstream router).

With such a small amount of VLANs I figured static routing would be a viable option with the default route going to our Internet firewall.

Any help would be appreciated.

Regards,
gp
4 REPLIES
Mohieddin Kharnoub
Honored Contributor

Re: Intervlan routing - small network

Hi

Since you have not enable routing on any of the 5400 switches, no routing between Vlans will occure.
Inter-Vlan routing can be enabled on all the 5400 switches by issuing the command:
5400(config)#ip routing
If you do this on all your 5400 switches, inter vlan routing will occure within each Switch.

Now:
To help each Vlan to reach same and/or other Vlan on other switch, you should tagg all Vlans 20,21,22 on the trunks between the switches, and keep the default-vlan untagged.

Internet:
add a default route to all the 5400 switches pointing to the internet router.

Good Luck !!!
Science for Everyone
George B. Park, III
Occasional Contributor

Re: Intervlan routing - small network

Hello again,

Sorry, I forgot to mention that I had enabled routing on all of the switches and tagged all VLANs, including VLAN1, on the trunks.

As it turns out I was (still am) having a problem with one VLAN which is based on a /27 network. All of the other networks are working fine, just this one is giving me issues.

Regards,
gp
André Beck
Honored Contributor

Re: Intervlan routing - small network

Hi George,

as always when configuring routed networks, setting up the routing itself is rather easy. In your case, defining the VLANs, adding switch virtual interfaces to them and making sure the VLANs are populated (having either access ports or tagged links to other switches) will suffice to establish the necessary connected routes. If still something doesn't work, it's either a failure in that setup (typo in addresses, mising tag on some inter switch link etc) or, more likely, a configuration error at the periphery - especially at the end systems. Most prominently, what is often forgotten is to configure all end systems with their respective default gateway.

Which of the switch virtual interface IP addresses do you use as the gateways in the VLANs?

BTW, given that you have three of them, you could consider to make them redundant using VRRP. I'd make the core box master and both of the others backup, so your routing will survive even a major hickup, provided the remaining infrastructure still has connectivity. In this case, I'd also establish OSPF between all of them, though it technically is not really necessary in this simple topology.

HTH,
Andre.
Mohieddin Kharnoub
Honored Contributor

Re: Intervlan routing - small network

Hi

Can you attach a copy of the configuration you have, and which Vlan is not working with you.

Good Luck !!!
Science for Everyone