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January 2007

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BGP routes persist in kernel
by Aaron Wirtz 05 Jan '07

05 Jan '07

I have a test setup involving 2 machines running BIRD, communicating routes via BGP. When trying to integrate to the Linux kernel routing table, I am having some problems. While BIRD is running, it adds BGP-learned routes to the kernel route table properly (also properly preferring the local device route 10.0.1.0/24 over the BGP-learned route 10.0.1.0/24). But when BIRD shuts down, it removes the device route 10.0.1.0/24 from the kernel table, then installs the BGP route 10.0.1.0/24 instead, and leaves the other BGP-learned routes in the kernel instead of cleaning them. I have attached the configuration and debugging output showing this problem. Maybe there is something obvious I am overlooking? -Aaron Config: router id 62.168.0.1; protocol device { debug all; scan time 10; } protocol direct { debug all; } protocol kernel { debug all; persist no; kernel table 254; learn; scan time 10; import all; export all; } protocol bgp { debug all; import all; export all; local as 123; neighbor 10.0.1.126 as 5; } Log: Lines marked "joda#" are commands I typed in the shell. Lines marked "bird>" are commands I typed to birdc. Lines marked "bird:" are debug output from bird. All other lines are the immediate output of a command I typed. joda# cat /proc/version Linux version 2.6.15-27-amd64-generic (buildd@king) (gcc version 4.0.3 (Ubuntu 4.0.3-1ubuntu5)) #1 SMP PREEMPT Fri Dec 8 17:50:54 UTC 2006 joda# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 10.0.1.1 0.0.0.0 UG 0 0 0 eth0 joda# bird -d bird: device1: Initializing bird: direct1: Initializing bird: kernel1: Initializing bird: bgp1: Initializing bird: device1: Starting bird: device1: Scanning interfaces bird: device1: State changed to feed bird: direct1: Starting bird: direct1: State changed to feed bird: kernel1: Starting bird: kernel1: State changed to feed bird: bgp1: Starting bird: bgp1: State changed to start bird: device1: State changed to up bird: direct1 < primary address 127.0.0.0/8 on interface lo added bird: direct1 > added [best] 127.0.0.0/8 dev lo bird: direct1 < primary address 10.0.1.0/24 on interface eth0 added bird: direct1 > added [best] 10.0.1.0/24 dev eth0 bird: direct1: State changed to up bird: kernel1: Connected to table master bird: kernel1 < added 10.0.1.0/24 dev eth0 bird: kernel1 < added 127.0.0.0/8 dev lo bird: kernel1: State changed to up bird: bgp1: Connect delayed by 5 seconds bird: kernel1: Scanning routing table bird: kernel1: 0.0.0.0/0: [alien] created bird: kernel1: Pruning table master bird: kernel1: Pruning inherited routes bird: kernel1 > added [best] 0.0.0.0/0 via 10.0.1.1 on eth0 bird: kernel1 < added 0.0.0.0/0 via 10.0.1.1 on eth0 joda# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 10.0.1.1 0.0.0.0 UG 0 0 0 eth0 joda# birdc BIRD 1.0.11 ready. bird> show route 0.0.0.0/0 via 10.0.1.1 on eth0 [kernel1 12:34] (10) 10.0.1.0/24 dev eth0 [direct1 12:34] (240) 127.0.0.0/8 dev lo [direct1 12:34] (240) bird: bgp1: Connecting to 10.0.1.126 from local address 10.0.1.10 bird: device1: Scanning interfaces bird: kernel1: Scanning routing table bird: kernel1: 0.0.0.0/0: [alien] seen bird: kernel1: Pruning table master bird: kernel1: Pruning inherited routes bird: bgp1: Incoming connection from 10.0.1.126 port 33378 bird: bgp1: Sending OPEN(ver=4,as=123,hold=240,id=3ea80001) bird: bgp1: Got OPEN(as=5,hold=240,id=3ea80002) bird: bgp1: Connection collision, giving up the other connection bird: bgp1: Sending KEEPALIVE bird: bgp1: Got KEEPALIVE bird: bgp1: State changed to feed bird: bgp1: Connected to table master bird: bgp1 < added 0.0.0.0/0 via 10.0.1.1 on eth0 bird: bgp1: Sending UPDATE bird: bgp1 < added 10.0.1.0/24 dev eth0 bird: bgp1: Sending UPDATE bird: bgp1 < out of scope 127.0.0.0/8 dev lo bird: bgp1: State changed to up bird: bgp1: Got UPDATE bird: bgp1 > added 10.0.1.0/24 via 10.0.1.126 on eth0 bird: bgp1: Got UPDATE bird: bgp1 > added [best] 10.1.2.0/24 via 10.0.1.126 on eth0 bird: kernel1 < added 10.1.2.0/24 via 10.0.1.126 on eth0 bird: bgp1 < rejected by protocol 10.1.2.0/24 via 10.0.1.126 on eth0 bird: bgp1: Got UPDATE bird: bgp1 > added [best] 10.0.7.0/24 via 10.0.1.126 on eth0 bird: kernel1 < added 10.0.7.0/24 via 10.0.1.126 on eth0 bird: bgp1 < rejected by protocol 10.0.7.0/24 via 10.0.1.126 on eth0 bird: bgp1: Got UPDATE bird: bgp1 > added [best] 10.9.8.0/24 via 10.0.1.126 on eth0 bird: kernel1 < added 10.9.8.0/24 via 10.0.1.126 on eth0 bird: bgp1 < rejected by protocol 10.9.8.0/24 via 10.0.1.126 on eth0 joda# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.7.0 10.0.1.126 255.255.255.0 UG 0 0 0 eth0 10.0.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 10.9.8.0 10.0.1.126 255.255.255.0 UG 0 0 0 eth0 10.1.2.0 10.0.1.126 255.255.255.0 UG 0 0 0 eth0 0.0.0.0 10.0.1.1 0.0.0.0 UG 0 0 0 eth0 bird> show route 0.0.0.0/0 via 10.0.1.1 on eth0 [kernel1 12:34] (10) 10.0.1.0/24 dev eth0 [direct1 12:34] (240) via 10.0.1.126 on eth0 [bgp1 12:34] (100) [AS5i] 10.1.2.0/24 via 10.0.1.126 on eth0 [bgp1 12:34] (100) [AS5i] 10.0.7.0/24 via 10.0.1.126 on eth0 [bgp1 12:34] (100) [AS5i] 10.9.8.0/24 via 10.0.1.126 on eth0 [bgp1 12:34] (100) [AS5i] 127.0.0.0/8 dev lo [direct1 12:34] (240) bird: device1: Scanning interfaces bird: kernel1: Scanning routing table bird: kernel1: 10.0.7.0/24: seen bird: kernel1: 10.9.8.0/24: seen bird: kernel1: 10.1.2.0/24: seen bird: kernel1: 0.0.0.0/0: [alien] seen bird: kernel1: Pruning table master bird: kernel1: Pruning inherited routes joda# killall bird bird: Shutting down bird: device1: Unconfigured bird: device1: Shutting down bird: direct1 < primary address 127.0.0.0/8 on interface lo removed bird: kernel1 < removed 127.0.0.0/8 dev lo bird: bgp1 < removed 127.0.0.0/8 dev lo bird: bgp1: Sending UPDATE bird: direct1 > removed [sole] 127.0.0.0/8 dev lo bird: direct1 < primary address 10.0.1.0/24 on interface eth0 removed bird: kernel1 < replaced 10.0.1.0/24 via 10.0.1.126 on eth0 bird: bgp1 < rejected by protocol 10.0.1.0/24 via 10.0.1.126 on eth0 bird: bgp1 < removed 10.0.1.0/24 dev eth0 bird: bgp1: Sending UPDATE bird: direct1 > removed [replaced] 10.0.1.0/24 dev eth0 bird: bgp1: Neighbor lost bird: bgp1: State changed to flush bird: bgp1: Sending NOTIFICATION(code=6.0) bird: device1: State changed to flush bird: direct1: Unconfigured bird: direct1: Shutting down bird: direct1: State changed to flush bird: kernel1: Unconfigured bird: kernel1: Shutting down bird: kernel1: Flushing kernel routes bird: kernel1: State changed to flush bird: bgp1: Unconfigured bird: kernel1 > removed [sole] 0.0.0.0/0 via 10.0.1.1 on eth0 bird: bgp1 > removed [sole] 10.0.1.0/24 via 10.0.1.126 on eth0 bird: bgp1 > removed [sole] 10.1.2.0/24 via 10.0.1.126 on eth0 bird: bgp1 > removed [sole] 10.0.7.0/24 via 10.0.1.126 on eth0 bird: bgp1 > removed [sole] 10.9.8.0/24 via 10.0.1.126 on eth0 bird: bgp1: State changed to down bird: device1: State changed to down bird: direct1: State changed to down bird: kernel1: State changed to down bird: System shutdown completed joda# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.7.0 10.0.1.126 255.255.255.0 UG 0 0 0 eth0 10.0.1.0 10.0.1.126 255.255.255.0 UG 0 0 0 eth0 10.9.8.0 10.0.1.126 255.255.255.0 UG 0 0 0 eth0 10.1.2.0 10.0.1.126 255.255.255.0 UG 0 0 0 eth0 0.0.0.0 10.0.1.1 0.0.0.0 UG 0 0 0 eth0 P.S. Also, BIRD did not seem to use the proper kernel routing table by default. I had to manually specify "kernel table 254" in the config.

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