Differences

This shows you the differences between two versions of the page.

--- bgp_communities_in_practice [2014/01/12 00:07] – samer
+++ bgp_communities_in_practice [2014/01/12 09:19] – samer
@@ Line 7: / Line 7: @@
 [{{ :commbgp-1.png?direct&500 | Figure 1. BGP community illustration}}]
-  * The client announces the prefix 10.1.2.0/24 with eBGP on the primary link toward NR-1 with a community attribute ''2200:610''.
+  - The client announces the prefix 10.1.2.0/24 with eBGP on the primary link toward NR-1 with a community attribute ''2200:610''.
-  * The client announces 10.1.2.0/24 on the backup link toward NR-2 with a community attribute ''2200:590''.
+  - The client announces 10.1.2.0/24 on the backup link toward NR-2 with a community attribute ''2200:590''.
-  * RENATER receives the same prefix (with eBGP) with two different communities and applies the following policy when announcing the prefix inside its network with iBGP :
+  - RENATER receives the same prefix (with eBGP) with two different communities and applies the following policy when announcing the prefix inside its network with iBGP :
-    * If the community attribute matches 2200:610, the local preference attribute in the iBGP announcement is fixed to ''p''.
+    - If the community attribute matches 2200:610, the local preference attribute in the iBGP announcement is fixed to ''p''.
-    * If the community attribute matches 2200:590, the local preference attribute in the iBGP announcement is fixed to ''p'''.
+    - If the community attribute matches 2200:590, the local preference attribute in the iBGP announcement is fixed to ''p'''.
-  * Therefore, NR-1 announces 10.1.2.0/24 in iBGP with a local preference p whereas NR-2 announces the same prefix with a local preference ''p'''.
+  - Therefore, NR-1 announces 10.1.2.0/24 in iBGP with a local preference p whereas NR-2 announces the same prefix with a local preference ''p'''.
-  * By choosing p' (we can assume that ''p = 610'' and ''p' = 590''), RENATER ensures that all its iBGP routers prefer the exit NR-1 to reach the client network and implement this information in their routing table.
+  - By choosing p' (we can assume that ''p = 610'' and ''p' = 590''), RENATER ensures that all its iBGP routers prefer the exit NR-1 to reach the client network and implement this information in their routing table.
 With this configuration, all the traffic going to the client network is forwarded by RENATER on the primary link. Note that whenever this link goes down, the BGP selection process chooses the next best announcement (lower local preference) and forwards the traffic on the backup link.