Inter-AS

Inter-AS Option B – Revisited

Consider the topology below.

Watch the video below or download and watch it on your iphone.

Option C – Revisited

Its been a while since I looked at this so here is a refresher.
Consider the topology below.

LDP is configured between RR3 and R1 and also between R2 and RR4.
EBGP with label advertisement is configured between R1 and R2.
The interesting this to notice here is that the label advertised between the EBGP peers is actually taken [...]

ISIS level-1, level-2 areas, ISIS redistribution and ISIS default route origination.

I’m going to cover following three things in this post.

Level-1, Level-1-2 and Level-2-only routers.  How to configure and what is the att bit
Investigate the default behavior of the various levels with respect to routing updates.  ie are level-2 prefixes by default advertised to level-1 routers.
Finally we will cover how to originate a default route within [...]

Inter AS MPLS VPN Option B, 2a – Packet Capture

I’ve setup the topology below.

I configured a loopback address with ip address 10.10.10.10 on PE1 and put it inside the VRF for VPN A.  One PE1 I could see the VPN label being generated by BGP as below.
sh ip bgp vpnv4 all labels
Network          Next Hop      In label/Out label
Route Distinguisher: 65300:1 (CUST)
10.10.10.10/32   0.0.0.0         19/nolabel
As you can [...]

Inter AS MPLS VPN Option C – Packet Capture

I setup the following topology.

I configured a loopback address with ip address 10.10.10.10 on PE1 and put it inside the VRF for VPN A.  One PE1 I could see the VPN label being generated by BGP as below.
sh ip bgp vpnv4 all labels
Network          Next Hop      In label/Out label
Route Distinguisher: 65300:1 (CUST)
10.10.10.10/32   0.0.0.0         19/nolabel
As you can [...]

Non VPN transit providers – Option 4?

There can be cases where two MPLS VPN service providers would like to deliver an MPLS VPN service to a customer using a non-VPN transit provider ie this non-VPN transit provider has an MPLS infrastructure, but does not deliver MPLS VPN services.
This architecture is sometimes referred to as Option 4(This is not mentioned in section [...]

Forwarding MPLS traffic over a non LDP interface

mpls bgp forwarding
*To enable an interface to receive Multiprotocol Label Switching (MPLS) packets when the signaling of MPLS labels is through the use of the Border Gateway Protocol (BGP), use the mpls bgp forwarding command in interface configuration mode. To disable an interface from receiving MPLS packets when the signaling of MPLS labels is through [...]

Inter-AS MPLS VPN Option C

Option C is the most complex of the three inter-AS MPLS VPN options, however its complexity has significant benefits in that it scales well.
However there are some trust issues which need to be overcome.  Usually this Option is not implemented unless you have a merger for example and two ASs need to provide an MPLS [...]

Inter-AS MPLS VPN Option b – Type 2a

Inter AS MPLS VPN Option b has three options as described below.
In the first option ie 2a an MP-eBGP session is configured between ASBRs to exchange VPNv4 prefixes.
The Link between the ASBRs does NOT run LDP/TDP and does not require an IGP.
The link is a straight forward point to point IP link.
A sample topology can [...]

Inter-AS MPLS VPN Option b – Type 2b

Inter AS MPLS VPN Option b has three options as described below.
In the second option ie 2b an MP-eBGP session is configured between ASBRs to exchange VPNv4 prefixes.
The Link between the ASBRs does NOT run LDP/TDP and does not require an IGP.
The link is a straight forward point to point IP link.
A sample topology can [...]