VLAN routing Problem

20 pts.
Tags:
Cisco 2511
Cisco Routers
L3 Switches
Routing
Switches
VLAN
VLAN management
Hi all

I have a situation here, I have created some VLANs on a L3 switch(Nortel), no problem with this. Inter vlan routing is taking place over here as well.

I have connected this L3 with a 2511 Cisco router. Here I want to mention one thing that all the VLANs can ping the outgoing port of the router. No problem here also.

Now why I have put the router I am telling you , to get the service of OSPF. Because this L3 doesn't have ospf support. And I have a device which is a NortelPassport which having all the WAN links and it is at the far end running OSPF. So I had to put this cisco router at the middle. Now Passport and the Router is communicating fineover OSPF.

But my actuall problem is, except for the one vlan which is on the same subnet can only get to the WAN link but others not, and at the same time I can't add diffenent routes for the vlans on the passpiort. so how can I get to the WAN links with my vlans.

I know the question is big but if any one can help me out I would be greatfull to him because I stuck overhere.

Please please please help me out.

write something over here or can mail me at pritam.banerjee1@gmail.com

Thanks in advance.

Pritam.



Software/Hardware used:
Nortelpassport 7440, L3 Switch 5500 series Nortel, Cisco router 2511.
ASKED: August 14, 2009  6:04 PM
UPDATED: October 27, 2010  4:58 AM

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How have you configured the router ?

Post a copy of the config, removing any passwords, and other sensitive information, and then we can get a better idea of what the problem might be. Also a simple diagram would help to clarify your description.

My thoughts are that the router needs to connect to the L3 switch using a VLAN trunk. This is done using subinterfaces on the router, each with an IP address in it’s particular VLAN. Then you can distribute these subnets in OSPF, and pass the traffic from the router to each VLAN. But seeing the existing config, and a basic diagram will help a lot in sorting your problem.

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  • Pikupiku742
    I have configured the lan port of the router with an ip. which is in the same subnet of vlan 1 and the passport's lan port. you are telling that i need to create virtual interfaces in the router.ok but at that time i have to give the ips of the vlans in the subinterfaces of the router. that means the intervlan routing would happend on the router itself. Now i don't need a L3 switch l2 would do the perpose. so using l3 is a west. but i have to use the l3 over here. and at the same time vlans are not only talking to each other but also every vlan can ping the router interface. in that case i probably don't need a trunk route. but still i would try that once. don't take it otherwise I am just discussing. plz advice me. thanks.
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  • BlankReg
    If you want the router to send and receive OSPF then you need IP addresses in the subnets that you want to propogate to other routers. If you don't want the router to do the inter-vlan routing, then you can put access lists on each sub interface to stop that happening. But if you already allow inter-vlan routing on the L3 switch, you don't need to prevent it on the router. If the router is providing the OSPF information to the Passport, then the packets must route via the router, so it needs to be either the gateway for each subnet (VLAN) or there needs to be static routes on the L3 switch, to say that the router is the path towards the Passport. I think you may be better off just configuring some static routing on the Passport, for each of these VLANs, and not complicate it with the router and OSPF. If there are not too many VLANs, and they don't change, then I think that may be the better option for you. The Passport should be able to put these subnets into OSPF if there are other devices in the network that need to have access to or from these subnets. Just another thought.
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  • pkpatel1151
    You will need to create su-interfaces on router and identify vlan associated with that subinterface. For example, let's say you have two VLANs, VLAN 10 (IP 10.10.10.0/24) and VLAN 20 (IP 10.10.20.0). On your layer 3 switch, you'd need to create VLAN Interface, let's say VLAN 10 with IP in 10.10.10.0 network. Assume that the IP Address of your VLAN 10 interface is 10.10.10.1. You'd also need VLAN 20 interface, IP 10.10.20.1. Now the port on switch that connects to router need to be configured as trunk port. As for router config, let's assume port fastethernet 0/0 conencts to switch. In that case, you'd create subinterface f0/0.10 and f 0/0.20, assign an appropriate IP Address and identify encapsulation and VLAN. Sampel config on router is below. int f 0/0.10 encapsulation dot1q 10 ip address 10.10.10.254 255.255.255.0 int f 0/0.20 encapsulation dot1q 20 ip address 10.10.20.254 255.255.255.0
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