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MPLS VPN Option3

Hi All,
        I have been faced with a challenge in the last three days yet unresolved.
The issue has to do with Inter-AS Option3
I hope with my explanation you can have a good picture of the topology which goes as follows:
10 routers in total makes up the LAB.
R1 and R2 are CEs in AS1 while R9 and R10 are CEs in AS2. R1 and R9 are in the same VPN while R2 and R10 are in the second VPN.
R3=PE1 AS1......>R4=P RR AS1.....>R5=ASBR AS1 <===============>R6=ASBR AS2...>R7=P RR AS2.....R8=PE1 AS2.
I have advertised and redistributed where necesary, RR AS1------RR AS2. ASBRs to each other.
I can see the foreign ISP routes on both PE and P routers in either way, but yet the CEs aren't seeing the routes hence cannot reach each other.
I have attached the configs your your perusal, if further info is needed i will be glad to produce.
More so, this lab is taken from a Cisco press "MPLS configuration on Cisco IOS" CHP 7 page 307-315 by LL UL.
I hope someone out there can resolve where something vital is missing out?.
Many thanks in advance

6 Replies 6

Mohamed Sobair
Level 7
Level 7

Your Config Looks Ok,

Now, apart from Option 3 Iner-AS Architecture, be noted that an End to End LSP between ingress and Egress PE is required. and you have already LSP established and you recieved the routes on both PEs. Here, you need to check the AS-Override , with normal BGP config, Split-Horizon rule would prevent Vrf Cust_B from importing the routes into the CE because both ingress and Egress CE on the Same AS.

If its, then you need to add the following on both PEs,

router bgp x

address-family ipv4 vrf Cust_B

nei x.x.x.x as-override



which cisco devices can deploy MPLS VPN option C approach???? how about 3945 and 7204 routers??

Hi Yongki,

The C7600 supports Inter-AS Option C indeed. The new 3945 ISR routers supports Option A, B.



thx a lot.  for ur opinion just only new 3945 isr routers can support Option C.  and then, how about 7204 series, cuz you didnot mentioned, i wanna confirm this.


I am not quite sure about 7204 series, but however, looking at the feature navigator, the C7200 NPE-G2 can support Inter-As as well.



firstly of all, giving my gratitude for ur favor.  check the inter AS method out with Feature Navigator tool, i found out the result(as following website link) that is just only Option A&B approach support on 3945 isr and 7204 series.

meanwhile,  i created a new topic named "L2 mpls inter AS approach".  Would you like to have a hand to me further???

thx & b.rgs

tony xi