Gateway?

Gary Palmer gpalmer at freebsd.org
Sun May 18 01:39:54 UTC 2014


On Sat, May 17, 2014 at 04:17:12PM -0700, Ronald F. Guilmette wrote:
> 
> Forgive me, please for such a rudimentary sort of question.  I've
> been doing IP networking for more than 15 years, but I never really
> plumbed the depths, and thus I only know the basics.
> 
> Quite simply, I'd like to know if the defaultrouter= IPv4 address
> specified in my /etc/rc.conf file should be the same as whatever
> I normally see as the first hop in an outgoing traceroute.  I ask
> because for me these two are apparently not the same.  Here's what
> I have:
> 
> defaultrouter="69.62.255.254"
> 
> and here is one example of a recent outgoing traceroute:
> 
> % traceroute 74.125.239.148
> traceroute to 74.125.239.148 (74.125.239.148), 64 hops max, 52 byte packets
>  1  86.255-62-69.res.dyn.surewest.net (69.62.255.86)  28.884 ms  31.395 ms  30.024 ms
>  2  216.0.55.209 (216.0.55.209)  26.486 ms  26.024 ms  25.850 ms
>  3  ae1d0.mcr1.roseville-ca.us.xo.net (216.156.1.77)  25.384 ms  27.298 ms  27.060 ms
>  4  vb1510.rar3.sanjose-ca.us.xo.net (216.156.0.153)  27.289 ms  34.022 ms  36.213 ms
>  5  207.88.14.226.ptr.us.xo.net (207.88.14.226)  26.993 ms  26.567 ms  25.568 ms
>  6  216.156.84.30.ptr.us.xo.net (216.156.84.30)  24.800 ms  26.432 ms  25.845 ms
>  7  209.85.249.5 (209.85.249.5)  26.033 ms  110.066 ms  28.663 ms
>  8  66.249.95.31 (66.249.95.31)  26.985 ms  25.285 ms  28.066 ms
>  9  nuq05s02-in-f20.1e100.net (74.125.239.148)  26.895 ms  27.434 ms  27.063 ms

They could be using some kind of HSRP or VRRP, and the above behaviour would
be normal (at least it was the last time I ran HSRP).  You set the route to
the failover address, but traceroute sees the response from the actual 
interface address on whichever gateway handles the packet.

e.g. 

router 1 interface 0 has IP x.x.x.2 and is the HSRP master
router 2 interface 0 has IP x.x.x.3 and is the HSRP backup
HSRP IP is x.x.x.1

Traceroute out and you normally see the answer from the first hop as x.x.x.2

There are other tricks they could be doing as well which would also
give the above behaviour.  

Regards,

Gary


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