Facts about BGP weight attribute Cisco proprietary. Only available for Cisco routers, this attribute is not included in BGP update message. Because it is not included in update message, this attribute is only locally significant to one router. Because it is locally significant and only the configured router knows the weight, it is only viable … Continue reading BGP attributes: Weight
IP routing with BGP
Problem 1: Did not receive prefix advertised by BGP peer. R2#sh ip bgp summary BGP router identifier 22.214.171.124, local AS number 2 BGP table version is 1, main routing table version 1 Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 192.168.12.1 4 1 44 43 1 0 0 00:36:08 0 R2 did not … Continue reading IP routing with BGP
BGP: Route reflector
Split horizon Split horizon rule is to prevent routing loop. In iBGP a router which learns prefixes from a BGP speaker will not advertise to BGP speaker, this makes a full mesh iBGP peering necessary in order for other BGP speakers to know the route. The number of TCP sessions can be calculated with this … Continue reading BGP: Route reflector
MPLS Layer 3 VPN
Acknowledgement Without MR.Keith Barker's 21 minutes video instruction, constructing MPLS VPN lab will take a longer time. His 21 minutes video instruction summarizes all. MR. Keith Barker has amazing skills to translate complicated concepts into simpler and easier to understand concepts. Now it is clearer to me and I believe it will be easier on … Continue reading MPLS Layer 3 VPN
BGP: Injecting IGP route into BGP without redistribution
The diagram is complicated with an additional link, and instead of full BGP route in AS65000, the BGP route is propagated with the help of OSPF. In previous lab, the BGP full mesh was established by peering both subnets of a BGP router. However this step can be simplified by peering the BGP speaker's loopback … Continue reading BGP: Injecting IGP route into BGP without redistribution
BGP: Route filter with ip prefix-list
Using the same network diagram, I would want prefix 10.20.0.0 to be filtered from advertisement by the border iBGP routers (r1 and r3). Using prefix-list is a more granular method than using ACL with distribute-list. Hide r2 prefixes from r5 This has to be done at r3 as this is the router than is doing … Continue reading BGP: Route filter with ip prefix-list
BGP: Full mesh BGP without IGP
r1, r2 and r3 have full meshed BGP peering. No IGP was used. BGP synchronization Before a BGP route is advertised and added to the routing table, this route must be known via an IGP. For the case of AS65000, no IGP is used, only pure iBGP peering hence BGP synchronization will stop bgp speaker … Continue reading BGP: Full mesh BGP without IGP
From the above caption, you can see by default the traffic from AS64513 to AS64512 will transit over at AS65000 which can utilize 2Gbps, to use an optimize route between AS64512 and AS64513 is either change the AD of BGP (distance bgp <external distance> <internal distance> <local distance>, default 20 200 200 respectively) or use … Continue reading BGP backdoor
BGP: Load balancing using ebgp multihop and loopback interface.
1841-1 configuration 1841-1#sh run | s router bgp router bgp 64512 no synchronization bgp log-neighbor-changes network 172.16.1.0 mask 255.255.255.0 neighbor 126.96.36.199 remote-as 64513 neighbor 188.8.131.52 ebgp-multihop 2 neighbor 184.108.40.206 update-source Loopback64512 no auto-summary 1841-1#sh run | i ip route ip route 220.127.116.11 255.255.255.255 192.168.1.2 ip route 18.104.22.168 255.255.255.255 192.168.2.2 1841-2 Configuration 1841-2#sh run | s … Continue reading BGP: Load balancing using ebgp multihop and loopback interface.
Tshoot BGP: Path unchanged despite local preference has been modified.
All routers within their own AS has been configured with IGP, routers within their own AS are reachable to one another (imagine the above diagram is part of an AS network). The border routers are connected to each other AS and exchanging prefixes. As shown in the diagram, two paths have different bandwidth, suboptimal routing … Continue reading Tshoot BGP: Path unchanged despite local preference has been modified.