Cisco router and HP procurve vlan configuration problem

[Jani Munne]

Hi!

I'm having problems with configuring vlan's between Procurve switches and cisco router. Scenario goes as follows:

Two different networks, both will be in their on vlan, let's say vlan1 and vlan2. Both of these vlan's should be able to reach router and outside networks. I have got two 2524 switches and a fiberlink between those. Both switches have vlan1 and vlan2 ports -> I have to make a trunk. how should i do this (i mean those untagged/tagged positions?). Then there is a problem with switch to router link, which is the best/working encapsulation and in which routers you can configure encapsulation in subinterfaces?

[Jerome Henry]

SAy you have SW1 and SW2, with on both VLAN1 and VLAN2, assuming for example ports1-10 are on VLAN1, ports 11-20 on VLAN2.
Subnet1 is on VLAN1, Subnet2 on VLAN2.
All these ports must be UNTAGGED for the VLAN they belong to.
Then you have the port going to the router. It should be TAGGED to both VLANS in order of VLANs to access it.
As for encapsulation, it depends on your topology. If you get to the Internet, then RIP is due. If you are in an inside network, IGRP is more efficient.
HP has a good configuration example page for setting up. look at :
http://www.hp.com/rnd/support/config_examples/5300xl.htm

hth
J

[Ron Kinner]

You would be wise to avoid using VLAN1 on the trunk to the Cisco. VLAN1 is the 802.1q native VLAN so has no tagging. Some versions of the Cisco IOS do not understand this (prior to 12.1(3)T and look for tagging and get upset because there is no tagging. However, it can be done and the following link tells you most of what you need to know to connect up to the Cisco:

http://www.cisco.com/en/US/tech/tk389/tk390/technologies_configuration_example09186a00800949fd.shtml

I think it depends on your IOS rather than the router whether you can configure encapsulation on the subinterfaces. The example shows it on the subinterfaces.

I'd stick with 802.1q since it is non proprietary. That way if you decide to get a new switch or router from another manufacturer you won't have to redo both ends.

Ron

[Markku Leinio]

Jani,

about the encapsulation on subinterfaces. It is not supported in every Cisco router hardware. At least Cisco 2500 series and 1720 are not trunking capable (no subinterfaces or dot1q (802.1Q) encapsulation). With those (or other similar) routers you'll have to use one physical interface (in the router) for connecting each VLAN.

Otherwise you can use 802.1Q trunking between the switch and the router:

Router (IOS 12.1(3)T or newer):

int f0/0 (or other interface)
no shutdown
int f0/0.1
encapsulation dot1q 1 native
ip address
int f0/0.2
encapsulation dot1q 2
ip address

Router (other IOS):

int f0/0
ip address
no shutdown
int f0/0.2
encapsulation dot1q 2
ip address

Switch (interface a24 used for trunking to the router):

vlan 1
untagged a24
vlan 2
tagged a24

Use the latter (style) commands also to configure trunking between the two 2524s.

Whether to use tagged or untagged, that's up to you, basically. In Cisco devices all interfaces have always one VLAN as native (untagged), other VLANs are tagged. In Procurves you can use one VLAN as untagged ("native" in cisco language) in a trunk, if you want. Additional VLANs must be tagged in any case.

In the previous example, if you wanted to tag both VLANs 1 and 2, you can always configure the Cisco interface with a native vlan of 999, for example, and use tagging ("encapsulation dot1q ") for VLANs 1 and 2.