Time since path change: 1 minutes, 14 seconds Time since created: 3 minutes, 26 seconds Path option 10, type explicit PRIMARY (Basis for Setup, path weight 2)īandwidth: 0 kbps (Global) Priority: 7 7 Affinity: 0x0/0xFFFFĪutoRoute: enabled LockDown: disabled Loadshare: 0 bw-basedīandwidthOverride: disabled LockDown: disabled Verbatim: disabled Name: R2_t0 (Tunnel0) Destination: 5.5.5.5Īdmin: up Oper: up Path: valid Signalling: connected This will tie a backup path into this tunnel interface.Īfter the the tunnel has been defined, we should see it comming up and we can verify it: Its also worth pointing out that we tell this tunnel to request Fast Reroute capabilities. Instead we could have created a static route pointing toward the tunnel interface when going to 6.6.6.6. What this does is to modify the OSPF selection to prefer path’s “behind” and on R5 through the tunnel interface. We also specify that we want autoroute announce. We tell the tunnel to goto 5.5.5.5 which is R5’s loopback interface. R2(config-if)# tunnel mpls traffic-eng fast-reroute R2(config-if)# tunnel mpls traffic-eng path-option 10 explicit name PRIMARY R2(config-if)# tunnel mpls traffic-eng autoroute announce R2(config-if)# tunnel mode mpls traffic-eng R2(config-if)# tunnel destination 5.5.5.5 R2(config)#ip explicit-path name PRIMARY enable Now lets create the primary tunnel, which will be Tunnel0 on R2:įirst off, the explicit path definition to force R2 to go through R3 and to R5: Lets verify this behavior before starting with the TE part:Ģ 10.2.3.3 56 msec 68 msec 76 msecģ 10.3.5.5 76 msec 72 msec 72 msecĪlright, so the data is taking the path that we expect under normal circumstances. This will be my prefered data path and one i expect all data toward R6’s loopback0 will take comming from R1. In order to get Node-Protection we need to create a tunnel going from R2 -> R3 -> R5. To do this, i will protect router R3 through Fast Reroute. What I want to demonstrate is the Node-Protection feature. R1 and R6 has no MPLS knowledge and simply forwards ordinary IP packets. I have enabled MPLS on R2, R3, R4 and R5.
So take a look at our topology used to demonstrate Fast Reroute (FRR) Node-Protection.Īs can be seen, we are running a simple OSPF topology where all routers are in the backbone area 0.įollowing normal OSPF convergence rules, the path from R1’s loopback0 (1.1.1.1) to R6’s loopback0 (6.6.6.6) will go from R1 to R2 -> R3 -> R5 -> R6, because the alternative has slower links (serial). The data re-establish at the “next next-hop”, which is the router one step further down than the failed router (or the node you are protecting). Node-Protection protects against the failure of an entire router. The data path with Link-Protection re-establish at the same router, but through a different path. Link-Protection protects a single link from failure and reconverges on the other “side” of the link. Namely Link-Protection and Node-Protection. Now there’s two types of Fast Reroute (nothing is ever simple right?). You then “protect” this path by a backup tunnel that takes a different path. So the concept of Fast Reroute is to establish a primary tunnel for your traffic, which is the path you want it to take in a normal situation.
Even with very aggressive tuning of the IGP, this is still way slower than SONET/SDH APS.įor example, tuning OSPF to a 1 second dead-interval, this is still 20 times slower. Without Fast Reroute, we would need to wait on the IGP to converge before being able to forward packets. Obviously, such aggressive convergence times are needed primarily in Service Provider networks or institutions with very high demands. In this post i would like to demonstrate the concept of a well known MPLS TE (Traffic Engineering) feature, known as Fast Reroute.įast Reroute, as the name implies, is used to create an MPLS network, that has similar convergence properties of SONET/SDH APS of about 50 ms. Node protection using MPLS-TE Fast ReRoute
0 kommentar(er)
