[nycbug-talk] FreeBSD Dual homed
swygue at gmail.com
Thu Dec 20 16:48:46 EST 2007
Brian A. Seklecki wrote:
> Okay dual verizon adsl lines. A common question.
> I'm assuming that you're trying to serve certain services off-of
> 150.210.240/24 and wondering why packets from 3rd party nework sources
> get there but not reply.
The service in question is SSH, as you can see from my netstat output:
root sshd 609 4 tcp4 *:22 *:*
It's listening on all available interface, so I should be able to
connect from 150.210.240/24 or /150.210.160/24. I don't seem to have
this problem when one interface is configured on a private address
space. i.e. 192.168.2.0/24.
> There can only be one default gateway. The gateway selection decision
> is not based on any type of "state" table (by default), so:
> 1) A packet received on em0 with a foreign network source address and
> a destination address of 150.210.240.x/32 will be received,
> decapsulated, processed by the kernel -- the reply packet will be
> generated and transmitted out of em1 with a source address of
> 150.210.160.xxx/32 and a destination of [foreign].
> Its just the nature of the TCP/IP stack and "standard" routing.
> I've seen discussion on misc at openbsd.org on a pf(4) feature that
> somehow works around this.
>> Destination Gateway Flags Refs Use Netif
>> default 22.214.171.124 UGS 0 415 em1
>> 150.210.160/24 link#2 UC 0 0 em1
>> 150.210.240/24 link#1 UC 0 0 em0
>> 126.96.36.199 00:0c:29:62:78:63 UHLW 1 6
>> em0 547
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