05-30-2003 11:38 PM - edited 03-02-2019 07:46 AM
Belowing output was generated on the routeserver, both 61.140.0.0 and
218.14.0.0 belong to ChinaNET, but the route server choose diff
next hop for them, the complete "show ip bgp regexp _4813$" indicated
that there are about 4 next_hop to AS4813 from the view of this routeserver,
but I follow the bgp decision process, both MED, AS_PATH, LOC_PREF and
even origin, route age, there was other AS_PATH with lower router_ID,
I still cannot tell why these different decision are make,
someone can help me?
for example, there are both 8075 4134 4813 to this 2 prefixes,but under the
same parameters, route-server choose different for 61.140 and 218.14
show ip bgp regexp _4813$
BGP table version is 491942, local router ID is 198.32.162.100
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* 61.140.0.0/15 217.75.96.60 0 16150 8434 3549 4134 4813 i
* 194.85.4.249 0 3277 3267 3343 2603 1239 4134 4813 i
* 195.66.224.82 31502 0 4513 7018 7018 4134 4134 4813 i
* 129.250.0.85 12 0 2914 7018 4134 4134 4813 i
* 129.250.0.11 6 0 2914 7018 4134 4134 4813 i
* 213.140.32.146 0 12956 1239 4134 4813 i
* 213.200.87.254 80 0 3257 1239 4134 4813 i
* 203.62.252.26 0 1221 4637 4134 4813 i
* 216.140.8.59 3 0 6395 7018 4134 4134 4813 i
* 209.123.12.51 0 8001 7911 4134 4813 i
* 216.140.14.186 1974 0 6395 7018 4134 4134 4813 i
* 207.246.129.6 0 11608 4134 4813 i
* 206.186.255.223 0 2493 3602 1239 4134 4813 i
* 216.218.252.152 0 6939 4134 4813 i
* 209.244.2.115 0 0 3356 7018 4134 4134 4813 i
* 207.246.129.14 0 11608 4134 4813 i
* 216.218.252.145 0 6939 4134 4813 i
* 208.186.154.36 0 0 5650 7018 4134 4134 4813 i
* 208.186.154.35 0 0 5650 7018 4134 4134 4813 i
* 65.106.7.139 3 0 2828 4134 4813 i
* 216.18.63.137 0 6539 2914 7018 4134 4134 4813 i
* 207.46.32.32 0 8075 4134 4813 i
*> 64.200.199.3 0 7911 4134 4813 i
* 208.51.113.253 0 3549 4134 4813 i
* 207.172.6.221 6 0 6079 3356 7018 4134 4134 4813 i
* 66.185.128.48 14 0 1668 7018 4134 4134 4813 i
* 209.10.12.28 8203 0 4513 7018 7018 4134 4134 4813 i
* 216.191.65.118 0 15290 7018 4134 4134 4813 i
* 209.10.12.156 0 0 4513 7018 7018 4134 4134 4813 i
* 209.249.254.19 0 0 6461 4134 4813 i
* 144.228.241.81 4294967294 0 1239 4134 4813 i
* 154.11.98.18 0 852 1239 4134 4813 i
* 202.232.0.2 0 2497 4774 4134 4813 i
* 193.251.128.22 0 5511 4134 4813 i
* 154.11.63.86 0 852 1239 4134 4813 i
* 208.172.146.2 0 3561 7018 4134 4134 4813 i
* 193.0.0.56 0 3333 3356 7018 4134 4134 4813 i
* 167.142.3.6 0 5056 1239 4134 4813 i
* 196.7.106.245 0 2905 701 7018 4134 4134 4813 i
* 207.45.223.244 0 6453 7018 4134 4134 4813 i
* 64.200.199.4 0 7911 4134 4813 i
* 192.205.31.33 0 7018 4134 4134 4813 i
* 64.50.230.1 0 4181 3356 7018 4134 4134 4813 i
* 64.50.230.2 0 4181 3356 7018 4134 4134 4813 i
* 204.29.239.1 0 6066 701 7018 4134 4134 4813 i
* 204.42.253.253 2 0 267 2914 7018 4134 4134 4813 i
####################################################
* 218.14.0.0/15 217.75.96.60 0 16150 8434 3257 1239 4134 4134 4134 4134 4134 4813 i
* 194.85.4.249 0 3277 8482 2578 702 701 7018 4134 4134 4813 i
* 195.66.224.82 31502 0 4513 7018 7018 4134 4134 4813 i
* 129.250.0.85 12 0 2914 7018 4134 4134 4813 i
* 129.250.0.11 6 0 2914 7018 4134 4134 4813 i
* 196.7.106.245 0 2905 701 7018 4134 4134 4813 i
* 209.161.175.4 0 14608 3356 7018 4134 4134 4813 i
* 209.244.2.115 0 0 3356 7018 4134 4134 4813 i
* 216.218.252.152 0 6939 4134 4813 i
* 206.186.255.223 0 2493 3602 1239 4134 4134 4134 4134 4134 4813 i
* 195.219.96.239 0 8297 6453 1239 4134 4134 4134 4134 4134 4813 i
* 193.0.0.56 0 3333 3356 7018 4134 4134 4813 i
* 203.62.252.26 0 1221 4637 4134 4813 i
* 66.185.128.48 14 0 1668 7018 4134 4134 4813 i
* 209.10.12.125 0 0 4513 7018 7018 4134 4134 4813 i
* 209.10.12.28 8203 0 4513 7018 7018 4134 4134 4813 i
* 207.172.6.173 31 0 6079 701 7018 4134 4134 4813 i
* 216.18.63.137 0 6539 2914 7018 4134 4134 4813 i
* 202.249.2.86 0 7500 2516 4134 4813 i
* 193.251.128.22 0 5511 4134 4813 i
* 64.200.199.3 0 7911 4134 4813 i
* 154.11.98.18 0 852 3561 7018 4134 4134 4813 i
* 154.11.63.86 0 852 3561 7018 4134 4134 4813 i
* 213.140.32.146 0 12956 209 4134 4813 i
* 216.218.252.145 0 6939 4134 4813 i
* 144.228.241.81 4294967294 0 1239 4134 4134 4134 4134 4134 4813 i
* 4.0.4.90 1190 0 1 3356 7018 4134 4134 4813 i
* 207.246.129.6 0 11608 4134 4813 i
* 216.140.2.59 981 0 6395 7018 4134 4134 4813 i
* 209.249.254.19 0 0 6461 4134 4813 i
* 64.200.199.4 0 7911 4134 4813 i
* 65.106.7.139 3 0 2828 4134 4813 i
* 157.130.182.254 1065 0 19092 7018 4134 4134 4813 i
* 216.140.8.59 3 0 6395 7018 4134 4134 4813 i
* 207.172.6.221 6 0 6079 3356 7018 4134 4134 4813 i
* 209.10.12.156 0 0 4513 7018 7018 4134 4134 4813 i
* 213.200.87.254 80 0 3257 1239 4134 4134 4134 4134 4134 4813 i
*> 207.46.32.32 0 8075 4134 4813 i
* 64.50.230.1 0 4181 3356 7018 4134 4134 4813 i
* 216.191.65.118 0 15290 7018 4134 4134 4813 i
* 209.123.12.51 0 8001 7911 4134 4813 i
* 134.55.20.229 0 293 7018 4134 4134 4813 i
* 208.172.146.2 0 3561 7018 4134 4134 4813 i
* 216.191.65.126 0 15290 7018 4134 4134 4813 i
* 64.50.230.2 0 4181 3356 7018 4134 4134 4813 i
* 207.45.223.244 0 6453 1239 4134 4134 4134 4134 4134 4813 i
* 216.140.14.186 1974 0 6395 7018 4134 4134 4813 i
* 208.186.154.35 0 0 5650 7018 4134 4134 4813 i
* 208.186.154.36 0 0 5650 7018 4134 4134 4813 i
* 141.142.12.1 0 1224 38 6325 209 4134 4813 i
* 208.51.113.253 0 3549 7018 4134 4134 4813 i
* 204.29.239.1 0 6066 701 7018 4134 4134 4813 i
* 167.142.3.6 0 5056 1239 1239 1239 4813 i
* 192.205.31.33 0 7018 4134 4134 4813 i
05-30-2003 11:46 PM
test
05-31-2003 05:25 AM
It's probably med inconsistency, but without full information for one of the routes in question, it's hard to tell. Check this link:
http://www.cisco.com/warp/public/459/25.shtml
And see if it answers your question.
Russ
05-31-2003 06:07 AM
I have checked the MED, LOC_PREF,both are set to 0 on routes with as path
of the same length, and the route generated at the same time
05-31-2003 01:27 PM
It could be that the router is configured to ignore router ID in the decision process. This is sometimes done to avoid flapping routes based on router ID. If this is the case then the decision process depends on the order in which the paths were received. The routes may have both been entered into the routing table 2 days and 2 hours ago, but that doesn't imply that the BGP paths for these routes were received at the same instant in time.
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