Pinging

samxd

Hello there

I have a quick question,

Why is that i can only ping address on my subnet?

For example, i have a ruoter conected to a switch and the switch to my pc. I can ping the interface of the router that is connected to my switch but not the interface 0/1 of that router that is for another subnet. I cant even ping another switch located in that other subnet on the other side of the router.

thanks in advance

EdTheLad

Think what happens when you send a ping.An arp request is sent to determine the destination mac address for the destination ip address.Since no device on the local subnet has the ip address of the remote interface an arp response is never received.
If you had configured the default gateway on your pc to be the ip address of the local router interface, the ping would have been addressed with a destination mac address of the local routers interface,when received on the router interface its processed at layer 2 and then passed to layer 3.Since the destination ip address is on a local interface the ping is sucessful and a reply is sent.

Plazma

Your default gateway has to know how to get to both destinations/subnets.

samxd

thank you very much.

I think i got it now, i need to assign a default-gateway to my pc, i forgot about that. I also assigned the default gateway for the swtich to be the router interface connected to it. Is this correct?

EdTheLad

samxd wrote:

thank you very much.

I think i got it now, i need to assign a default-gateway to my pc, i forgot about that. I also assigned the default gateway for the swtich to be the router interface connected to it. Is this correct?

The question is, why do you want a default gateway configured on your switch? for remote management?

samxd

i am assuming that in order for the switch to reach an address that is not on its subnet, it can use its deafult gateway to go to it... is this correct?

JavonR

samxd wrote:

i am assuming that in order for the switch to reach an address that is not on its subnet, it can use its deafult gateway to go to it... is this correct?

Nope, switches don't have layer3 functionality (unless you are using a layer 3 switch). The ip default-gateway command is mostly for enabling telnet/ssh access. This is why you set the default gateway on your computer, it takes care of the layer 3 stuff. Hope that helps.

samxd

ok that makes sence now, so we assign it a default gateway so that it can communicate back to the one telnetting to it.?

JavonR

Right, this is because you are communicating with the switch via IP directly.

Netwurk

and make sure your firewall does not block pings if you are trying to reach a Windows PC. Almost all XP and Vista boxes block ping by default.

Kind of dumb for Microsoft to do that, since there are a lot of better ways to stop "ping of death" attacks. But they do a lot of things that make no sense. Keeps us all employed I guess. If their OS worked flawlessly they wouldn't need us.

samxd

LOL