BGP Subnet – Can Same Subnet Be Used in Two Locations with BGP?

bgpmplsroutingsubnet

I am not sure this is possible, but I'd like to route traffic over an MPLS network using BGP to different locations, but use the same subnet.

We have an east coast and west coast location. Each of these locations has a VPN connection to a common 3rd party location via VPN. The subnet of this 3rd party is 10.5.5.0/24. We have a number of locations throughout the United States all connected through an MPLS network. I would like those locations to use either the east or west coast VPN.

How could I route some traffic to 10.5.5.0/24 in one location and some to the other? I read it might be possible using different AS numbers and one would need to coordinate this with the MPLS provider, but really not sure.

Any ideas? If you need more detail please let me know. I am not a network engineer by trade and really just hack my way through this stuff.

Thank you!

Best Answer

MP BGP EVPN allow you to extend L2 over any IP network. It encapsulates L2 traffic inside UDP. Although I'm not sure how well it works with large geographic separation. But check it out nevertheless: https://www.juniper.net/documentation/en_US/junos/topics/concept/vxlan-evpn-integration-overview.html

There are also DCI specific technologies such as OTV, which encapsulates L2 inside MPLS inside GRE. This is however a proprietary technology from cisco: http://blog.ine.com/2010/02/15/what-is-overlay-transport-virtualization/

Related Solutions

Cisco – traffic engineering – policies for BGP vs static routes

Policy-based routing works great for this. I recently did this to slowly cut over a hospital to a new internet edge one internal subnet at a time in exactly this way.

ip access-list extended PBR_SUBNETS
 permit ip 172.16.1.0 0.0.0.255 any
!
route-map POLICY_ROUTE permit 10
 match ip address PBR_SUBNETS
 set ip next-hop 192.168.1.2

The above will redirect all packets from 172.16.1.0/24 to the IP address specified in the route-map. Change both as needed to fit your situation.

Apply this policy to the router interface that's facing your internal subnets.

interface GigabitEthernet0/1
 ip policy route-map POLICY_ROUTE

This route-map will set the next hop for all permitted traffic, regardless of the routing table. (Use of the "default" keyword can get around this but doesn't sound like you need to) This means that your static route is probably not needed for this purpose, but you can leave it in there as a fallback in case BGP fails.

FYI - the way I did this was to enter the entire configuration, live, during the day, but with no entries in the access list. Since nothing matches, obviously, all traffic behaves normally, following the routing table. This provides for a very easy, testable, reversible framework for switching internal subnets over, since all it takes from this point is just to add them to the ACL.

MPLS Network Design: Ensuring a Correct Design

This is quite complex to answer in simple set of questions, but let's try:

Yes, it's possible to have internet connectivity by means of MPLS cloud, but it either means you need to self-deploy MPLS L3 VPN for yourself, or your MPLS cloud will be provided by upstream ISPs.
Usually, edge routers - the ones running MPLS, are distinct from L3 switches/routers in aggregation layer, specifically, that You also add firewalls to the picture. It's doable, but usually it's better to route at the switching layer not aggregation/edge layer.
You're trying to ask very specific configuration question, not specifically technology one. It's possible to separate VLANs by means of various techniques - splitting the access ports to access and trunk is very weak and unsecure method. Please take a look at Private VLANs as one way, the other would be the firewalling segment to take responsibilities of filtering traffic between hosts or networks.
Again, hard question. In this specific topology yes, they can be placed this way. Depending on the performance required or features required, they may however be required to be positioned in a different way.
"Common servers" availability will be governed by configuration, not topology. We have too little data right now to decide if that's feasible or not. MPLS can be used to transport traffic of different protocols, including IPv4 and IPv6.
Yes, it's possible to use IPsec over MPLS. IPsec is IP based, MPLS is transport technology for IP - be it IPv4 or IPv6.

Best Answer

Related Solutions

Cisco – traffic engineering – policies for BGP vs static routes

MPLS Network Design: Ensuring a Correct Design

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