Date: Sun, 31 Mar 2013 20:32:19 +0100 From: Richard Tector <richard@tector.org.uk> To: freebsd-net@freebsd.org Subject: Route next-hop interface behaviour Message-ID: <51588F43.7060609@tector.org.uk>
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Hi,
I'm not sure if it is expected behaviour but when configuring a static
route (default or otherwise) the outbound interface recorded in the
table does not update when the system's IP changes interface, even when
removing and re-adding it.
Fairly simple topology, system running 9.1-STABLE (30th March) with just
one of four 'em' interfaces in use - em0 with 10.0.2.199. Default route
to 10.0.2.1.
Whilst troubleshooting some odd TCP behaviour I thought I'd try a
different interface and so downed the active interface and brought up
one on a PCI card, and swapped the cable over:
# ifconfig em0 down
# ifconfig em2 inet 10.0.2.199/24
# ifconfig em2 up
#####
If I then ping an external host it shows as the destination network
being inaccessible:
root@daffy:~ # ping 212.23.6.76
PING 212.23.6.76 (212.23.6.76): 56 data bytes
ping: sendto: Network is down
#####
Can contact the next hop just fine:
root@daffy:~ # ping 10.0.2.1
PING 10.0.2.1 (10.0.2.1): 56 data bytes
64 bytes from 10.0.2.1: icmp_seq=0 ttl=64 time=0.211 ms
#####
Routing table shows that the default route is still bound to em0 even
though the next hop is on em2:
root@daffy:~ # netstat -rfinet -n
Routing tables
Internet:
Destination Gateway Flags Refs Use Netif Expire
default 10.0.2.1 UGS 0 3141 em0
^^^
10.0.2.0/24 link#4 U 1 255 em2
10.0.2.199 link#1 UHS 1 0 lo0
127.0.0.1 link#9 UH 0 0 lo0
#####
Removing the default route and re-adding also leaves it on the old
interface:
root@daffy:~ # route delete default
delete net default
root@daffy:~ # route add default 10.0.2.1
add net default: gateway 10.0.2.1
root@daffy:~ # netstat -rfinet -n
Routing tables
Internet:
Destination Gateway Flags Refs Use Netif Expire
default 10.0.2.1 UGS 0 0 em0
10.0.2.0/24 link#4 U 0 688 em2
10.0.2.199 link#1 UHS 1 0 lo0
127.0.0.1 link#9 UH 0 0 lo0
I can understand the initial problem, but surely when I re-add the route
it should do a lookup against the table for the next hop, ie.
10.0.2.0/24, and use the associated Netif?
What's interesting is that if I remove the IP configuration from em0 it
removes the default route above (even though the interface is downed).
Re-adding the route works.
Regards,
Richard
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