IMCP not returning

IMCP not returning

[Sadus .]

Hello,
I'm trying to ping to a host and its not answering from location 1, but
it is answering from location 2, now when i ping from location 1, i can
see on the host's logs that location 1 can reach the machine since i log
icmp pings.

i still can't get replies from the box on location1 (i can ping any
other machine on the net so my ISP doesn't block ICMPs)

Thanks
-- 
Sadus . <sadus@swiftbin.net>
Swiftbin.net

Re: IMCP not returning

[Jason Opperisano]

On Sat, Jun 11, 2005 at 06:37:33PM +0300, Sadus . wrote:
> Hello,
> I'm trying to ping to a host and its not answering from location 1, but
> it is answering from location 2, now when i ping from location 1, i can
> see on the host's logs that location 1 can reach the machine since i log
> icmp pings.
> 
> i still can't get replies from the box on location1 (i can ping any
> other machine on the net so my ISP doesn't block ICMPs)

you have a routing problem.  $host knows to get to $location_1, but
$location_1 doesn't know how to get back to $host (or has an invalid
route to to it).  start at $host with:

  ip route get $location_1

and follow the trail until it makes a wrong turn.

-j

--
"Quagmire: Hey Peter, you can't drink that outside. You're gonna end
 up in jail. And not the good jail you see on Cinemax. The man jail."
        --Family Guy

Re: IMCP not returning

[Jason Opperisano]

On Sat, Jun 11, 2005 at 11:58:25AM -0400, Jason Opperisano wrote:
> On Sat, Jun 11, 2005 at 06:37:33PM +0300, Sadus . wrote:
> > Hello,
> > I'm trying to ping to a host and its not answering from location 1, but
> > it is answering from location 2, now when i ping from location 1, i can
> > see on the host's logs that location 1 can reach the machine since i log
> > icmp pings.
> > 
> > i still can't get replies from the box on location1 (i can ping any
> > other machine on the net so my ISP doesn't block ICMPs)
> 
> you have a routing problem.  $host knows to get to $location_1, but
> $location_1 doesn't know how to get back to $host (or has an invalid
> route to to it). 

i transposed that.  i meant:  $location_1 knows how to get to $host,
but $host doesn't know how to get back to $location_1 (or has an invalid
route to to it).

but i got this part as i intended:

> start at $host with:
> 
>   ip route get $location_1
> 
> and follow the trail until it makes a wrong turn.

-j

--
"Peter: Well, fine. Until you put 'Gumbel 2 Gumbel' back on the air,
 I'm going on a hunger strike. Can you live with that? Huh, can you?"
 Peter: You gonna eat that stapler? 
 Network executive: Mr., you can't eat a... 
 Peter: Wanna split it?"
        --Family Guy

Re: IMCP not returning

[Sadus .]

This is what i'm getting:

debian:~# ip route get locationIP
locationIP dev eth1  src HostIP     
	cache  mtu 1500 advmss 1460 hoplimit 64



umm? 

On Sat, 2005-06-11 at 12:08 -0400, Jason Opperisano wrote:
> On Sat, Jun 11, 2005 at 11:58:25AM -0400, Jason Opperisano wrote:
> > On Sat, Jun 11, 2005 at 06:37:33PM +0300, Sadus . wrote:
> > > Hello,
> > > I'm trying to ping to a host and its not answering from location 1, but
> > > it is answering from location 2, now when i ping from location 1, i can
> > > see on the host's logs that location 1 can reach the machine since i log
> > > icmp pings.
> > > 
> > > i still can't get replies from the box on location1 (i can ping any
> > > other machine on the net so my ISP doesn't block ICMPs)
> > 
> > you have a routing problem.  $host knows to get to $location_1, but
> > $location_1 doesn't know how to get back to $host (or has an invalid
> > route to to it). 
> 
> i transposed that.  i meant:  $location_1 knows how to get to $host,
> but $host doesn't know how to get back to $location_1 (or has an invalid
> route to to it).
> 
> but i got this part as i intended:
> 
> > start at $host with:
> > 
> >   ip route get $location_1
> > 
> > and follow the trail until it makes a wrong turn.
> 
> -j
> 
> --
> "Peter: Well, fine. Until you put 'Gumbel 2 Gumbel' back on the air,
>  I'm going on a hunger strike. Can you live with that? Huh, can you?"
>  Peter: You gonna eat that stapler? 
>  Network executive: Mr., you can't eat a... 
>  Peter: Wanna split it?"
>         --Family Guy
> 
-- 
Sadus . <sadus@swiftbin.net>
Swiftbin.net

Re: IMCP not returning

[Jason Opperisano]

On Sat, Jun 11, 2005 at 07:29:49PM +0300, Sadus . wrote:
> This is what i'm getting:
> 
> debian:~# ip route get locationIP
> locationIP dev eth1  src HostIP     
> 	cache  mtu 1500 advmss 1460 hoplimit 64

that's not a complete entry, unless $locationIP is on the same layer 3
subnet as $HostIP.

like this output from my machine on 10.1.1.0/24 with IP 10.1.1.223:

$ ip route get 10.1.1.1
10.1.1.1 dev eth0  src 10.1.1.223
    cache  mtu 1500 advmss 1460 fragtimeout 64

a route get for an IP address not on the local segment would have a "via
$gateway_IP" part to it:

$ ip route get 4.2.2.2
4.2.2.2 via 10.1.1.1 dev eth0  src 10.1.1.223
    cache  mtu 1500 advmss 1460 fragtimeout 64

since you're not providing any actual IP information, i can't actually
help you, but if $locationIP is not on the same layer 3 subnet as
$HostIP, or is not *directly* reachable on eth1, someone has added a
faulty route to that box along the lines of this:

  ip route add $locationIP dev eth1

instead of:

  ip route add $locationIP via $gateway_IP

good luck figuring it out--you have all the tools at your hands now.

-j

--
"Peter: YEAH. I'm also addicted to boobies."
        --Family Guy