Service provider MPLS Layer-3 LAB

Here is the following topology:

 

Hostname	Administrative	Role
R1	Service provider	PE
R2	Service provider	P
R3	Service provider	PE
R4	Customer #1	CE
R5	Customer #2	CE
R6	Customer #1	CE
R7	Customer #2	CE
R8	Service provider	PE

 

Customer #1 has two sites: R4 and R6 both connected to the SP in single homed mode and using EIGRP as a CE to PE dynamic routing protocol.

R4#show ip route Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP        D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area        N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2        E1 - OSPF external type 1, E2 - OSPF external type 2        i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2        ia - IS-IS inter area, * - candidate default, U - per-user static route        o - ODR, P - periodic downloaded static route   Gateway of last resort is not set   D EX 192.168.61.0/24 [170/30720] via 10.1.34.3, 00:10:53, FastEthernet0/0 C    192.168.41.0/24 is directly connected, Loopback1      10.0.0.0/24 is subnetted, 2 subnets D EX    10.1.16.0 [170/30720] via 10.1.34.3, 1w3d, FastEthernet0/0 C       10.1.34.0 is directly connected, FastEthernet0/0

 We can see that R4 is learning network 192.168.61.0/24 from R6 using EIGRP.

Now customer #1 wants to get internet access although he doesn’t have a (physical) link to the internet or spare router to connect to, so the SP will have to provide him internet access through his backbone.

So our goal is to inject default route to customer #1 VRF.

In order to avoid advertising SP BGP router-id’s (loopback) and backbone link IP’s into customer VRF we would create a separate VRF which will hold default route to the global routing table and then we will do route leakage between customer #1 VRF and  this new VRF.

I have configured a new VRF on R8:

ip vrf INTERNET  rd 65002:8  route-target export 65002:888  route-target import 65002:888 !

And configured interface Fa2/0 in VRF INTERNET:

interface FastEthernet2/0  mac-address 0017.df3f.a832  ip vrf forwarding INTERNET  ip address 10.1.88.2 255.255.255.0  no ip redirects  no ip proxy-arp  duplex full  speed 100

Note that I changed the mac address of the interface.

Now interface Fa1/1 is in the global routing table:

interface FastEthernet1/1  ip address 10.1.88.1 255.255.255.0  no ip redirects  no ip proxy-arp  load-interval 30  duplex full  speed 100

 And now the BGP configuration between VRF INTERNET and the global routing table:

router bgp 65000  no synchronization  bgp router-id 8.8.8.8  bgp log-neighbor-changes  network 0.0.0.0  redistribute static  neighbor 2.2.2.2 remote-as 65000  neighbor 2.2.2.2 update-source Loopback0  neighbor 2.2.2.2 route-reflector-client  neighbor 2.2.2.2 send-community both  neighbor 2.2.2.2 soft-reconfiguration inbound  neighbor 10.1.88.2 remote-as 65002  neighbor 10.1.88.2 local-as 65001 no-prepend replace-as  neighbor 10.1.88.2 ebgp-multihop 5  neighbor 10.1.88.2 next-hop-self  neighbor 10.1.88.2 default-originate  default-information originate  no auto-summary  !  address-family vpnv4   neighbor 2.2.2.2 activate   neighbor 2.2.2.2 send-community both   neighbor 2.2.2.2 route-reflector-client  exit-address-family  !  address-family ipv4 vrf INTERNET   redistribute connected   redistribute static   neighbor 10.1.88.1 remote-as 65001   neighbor 10.1.88.1 local-as 65002 no-prepend replace-as   neighbor 10.1.88.1 ebgp-multihop 5   neighbor 10.1.88.1 activate   neighbor 10.1.88.1 next-hop-self   no synchronization   bgp router-id 10.1.88.2  exit-address-family

 

So now R8 has a BGP peering between VRF INTERNET and the global routing table:

R8#show ip bgp summary BGP router identifier 8.8.8.8, local AS number 65000 BGP table version is 13, main routing table version 13 2 network entries using 264 bytes of memory 2 path entries using 104 bytes of memory 11/2 BGP path/bestpath attribute entries using 1628 bytes of memory 2 BGP rrinfo entries using 48 bytes of memory 2 BGP AS-PATH entries using 48 bytes of memory 6 BGP extended community entries using 288 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory Bitfield cache entries: current 2 (at peak 3) using 64 bytes of memory BGP using 2444 total bytes of memory BGP activity 16/7 prefixes, 18/9 paths, scan interval 60 secs   Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd 2.2.2.2         4 65000     453     127       13    0    0 01:19:45        0 10.1.88.2       4 65002     116     119       13    0    0 01:17:52        1

Now we can advertise default route, from R8 global routing table to the customer VRF, using VRF INTERNET,

R8:

ip vrf INTERNET  rd 65002:8  route-target export 65002:888  route-target import 65002:888  route-target import 100:888

 And on R1:

ip prefix-list PL_NET6 permit 192.168.61.0/24 ! route-map VRF_BLUE_EXPORT permit 10  match ip address prefix-list PL_NET6  set extcommunity rt  100:888 ! route-map VRF_BLUE_EXPORT deny 999 ! ip vrf BLUE  rd 1:100  export map VRF_BLUE_EXPORT  route-target export 100:100  route-target import 100:100  route-target import 65002:888

 

Now when tracing to some unknown address from customer #1 R6 router:

R6#traceroute 8.8.8.8 source lo1   Type escape sequence to abort. Tracing the route to 8.8.8.8     1  *     10.1.16.1 20 msec 36 msec   2 10.1.12.2 [MPLS: Labels 17/24 Exp 0] 140 msec 72 msec 108 msec   3 10.1.88.2 [MPLS: Label 24 Exp 0] 72 msec 40 msec 44 msec   4 10.1.88.1 84 msec *  96 msec

 

We can see that we are reaching R8 global routing table hence we reach outside the VRF.

What I have done on R8 is a little bit tricky, i use one router with two different legs to create eBGP peer between them, in  this way I could made a VRF with default route injected in it without advertising all SP backbone IP’s and without the burden of managing static routes for return traffic.