ping stucks/hangs on PCI 3com NIC sk0 interface but works on builtin NIC

Faizan ul haq Muhammad faizi62 at hotmail.com
Thu Feb 26 05:30:36 PST 2009


Thanks dude, it helped me. if i configure the NICs with IPs belonging to different subnets, I get ping working locally.
I can see multiple routes for different subnets in NETSTAT too.
Now i assume that in order to configure the NICs with the same NETWORK and make them working i need to configure the System as router.

Anyways, for now Thanks for your help .. 

Regards
/Faizan



> From: lists at jnielsen.net
> To: faizi62 at hotmail.com
> Date: Wed, 25 Feb 2009 15:15:46 -0500
> CC: freebsd-questions at freebsd.org
> Subject: Re: ping stucks/hangs on PCI 3com NIC sk0 interface but works on	builtin NIC
> 
> On Wednesday 25 February 2009 01:11:42 pm Faizan ul haq Muhammad wrote:
> > > From: lists at jnielsen.net
> > > On Wednesday 25 February 2009 12:35:23 pm Faizan ul haq Muhammad 
> wrote:
> > > > Hi
> > > > I have two PCI NICs and one builtin NIC on freebsd 7.0
> > > > ifconfig shows information somthing like:
> > > >
> > > > bge0: flags=8843<UP, broadcast, runing, simplex, multicast>metric 0
> > > > mtu 1500 options=9b<RXCSUM,TXCSUM, VLAN_HWTAGGING. VLAN_HWCSUM>
> > > > ether 00:13:21:f8:7e:56
> > > > inet 192.168.0.1 netmask 0xffffff00 broadcast 192.168.0.255
> > > > media: Ethernet autoselect (none) status: no carrier
> > >
> > > This is NIC doesn't appear to be plugged in.
> >
> > no it is not plugged into any other yet and if i plug it and ping it
> > from an external machine, it works
> 
> That's good.
> 
> > > > sk0: flags=8843<UP, broadcast, runing, simplex, multicast>metric 0
> > > > mtu 1500 options=b<RXCSUM,TXCSUM, VLAN_MTU>
> > > > ether 00:0a:5e:1a:69:25
> > > > inet 192.168.0.2 netmask 0xffffff00 broadcast 192.168.0.255
> > > > media: Ethernet autoselect (none) status: no carrier
> > >
> > > Neither is this one.
> >
> > You are right, but it does not reply to ping even if i plug this to an
> > external system with crossover cable and ping from that PC.
> 
> Still not surprising. See below.
> 
> > that is the difference in behaviour of both NICs
> >
> > > > Note: bge0 is builtin NIC
> > > > sk0 is 3com PCI NIC
> > > >
> > > > now after configuration of IPV4 Addresses, when i verify the
> > > > configuration with ping
> > > >
> > > > if i ping bge0(ping 192.168.0.1) i get the response of success
> > > > but when i ping sk0 (ping 192.168.0.2) Ping gets stuck and gives no
> > > > response, neither it gives success or host unreachable or denied
> > > > kinda errors..
> > >
> > > Why do you want both interfaces to be configured on the same subnet?
> >
> > that is not required as such, I am just preparing the setup to use this
> > machine a bridge and configure dummynet on this machine.
> 
> You might try a different configuration for your testing. I suspect if you 
> changed the IP address of sk0 to 192.168.1.2 or similar it would behave 
> as you are expecting.
> 
> > > > it just hangs over there.. and i can juz see one line of ping
> > > > not proceeding anyway. and if I terminate it via CTRL C then i get
> > > > statistics sumthing like 3 packets sent, 0 received and 100%
> > > > loss...
> > >
> > > This is probably expected behavior. What does "netstat -rn" show? My
> > > guess is that the route for 192.168.0.0/24 is "link#1" aka bge0 and
> > > since it's not plugged in to anything that's as far as it gets.
> >
> > btu it does not show any other interface in netstat printout with this
> > -rn switch
> >
> > and can you explain, how this is the expected behavior then..?
> 
> There can only be one route at any time for any given network. When you 
> bring up bge0 with 192.168.0.1 a route is automatically created for 
> 192.168.0.0 pointing to that interface. When you then bring up sk0 with 
> 192.168.0.2 no additional route can be added for 192.168.0.0 since there 
> is already one present. Therefore ALL traffic destined for the 
> 192.168.0.0 network will go out via bge0.
> 
> In order to be able to ping 192.168.0.2 _locally_ you'd either need to 
> connect the interfaces with a crossover cable (well, crossover isn't 
> strictly necessary since gigabit ethernet adapters can figure it out on 
> their own..) OR plug both interfaces into a switch/hub. Ping packet goes 
> out bge0 (according to the route), across the wire and comes in on sk0 
> (destination address). The response would be delivered directly to bge0 
> (without going over the wire).
> 
> Similarly, in order to be able to ping 192.168.0.2 from a second machine 
> all _three_ interfaces would need to be connected to the same network 
> segment (via a switch/hub, etc). Ping packet goes out from peer, across 
> the wire and in on sk0 (destination address). Response goes out bge0 
> (according to route), across the other wire and back to the peer.
> 
> I hope this helps you make sense of things.
> 
> JN
> 
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