Cisco VRF


I have a Cisco router (c1921) that travels around the country and plugs into different networks (hotels, convention centers, etc..).  

We of course have issues when the DHCP WAN IP address we receive from the venue conflicts with the LAN networks.

We are thinking of using VRF to fix this issue.

I am looking for a good sample configuration with the WAN interface on the router is getting an IP address via DHCP (mostly private 172.16.x.x, 192.168.x.x and 10.x.x.x networks), and the LAN has multiple subinterfaces for dot1q VLANs.

I do have a Cisco EZVPN that connects to our datacenter, so this would still need to work.

Thank you!

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Craig BeckConnect With a Mentor Commented:
If your WAN is NOT configured in a VRF it won't interfere with a LAN interface which is in a VRF.

The problem there is that your LAN interface won't be able to route via the WAN interface.  The VRF membership dictates which interfaces are taking part in that routing instance.

You can configure a VPN and tie that to the VRF, and that can route via the WAN.
Craig BeckCommented:
How are you thinking of fixing this with VRF?

The above is a good example of ezvpn with vrf.

The only other piece to the puzzle would be to configure the outside interface with dhcp in the global routing table (with no vrf specified) and to apply the ezvpn vrf to the inside interface.
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chikagohAuthor Commented:
Craigbeck, With vrf you can have duplicate ip networks in different routing instances correct?
Craig BeckCommented:
But if you've only got one WAN link, with one IP address, how will VRF help?

Can you expand on what exactly you want to achieve using VRF?
Craig BeckCommented:
Yes you can have duplicate IP addresses in different VRFs, BUT if you only have one WAN address, what will VRF do for you?
chikagohAuthor Commented:
Craigbeck. I just don't want my wan(dhcp) to conflict with any of my LAN sub interfaces
Craig BeckCommented:
What I'm getting at is (as an example):

You have a single WAN link with IP
You have a LAN using IP range

How will VRF help to overcome this??

Maybe there's something missing from the OP, but are you suggesting that the LAN needs to route to a central office via EZ-VPN (therefore effectively bypassing the WAN routing)?

If so, rauenpc's example is what you need.  If not, VRF won't help.
chikagohAuthor Commented:
rauenpc: If the WAN interface (global routing table) gets a DHCP address that conflicts with a LAN VRF-lite interface, will there be a conflict?
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