Cannot ping ethernet0/0 of Cisco 2610 with DHCP

[Motopsycho]

Okay help me out here...I am currently connected to the ethernet port of a Cisco 2610 via x-over cable to my laptop. The router has no serial interface card and will be used only as a DHCP server. I have the DHCP pool configured in the router as well as the ethernet interface, however I cannot ping the ethernet interface of the router and vice-versa. The DHCP server works without an issue but why can't I ping? I'm thinking that the router does not know how to route the packets because it is acting as a default gateway for the DHCP host and the default route is the same. I'm not sure how this makes any sense. Can someone explain??

ervice timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Router
!
no logging console
!
ip subnet-zero
!
!
ip dhcp excluded-address 10.0.22.201 10.0.22.254
ip dhcp excluded-address 10.0.22.1 10.0.22.99
!
ip dhcp pool 0
network 10.0.22.0 255.255.255.0
domain-name xxxxxx.com
dns-server 10.0.2.225 10.50.1.3
netbios-name-server 10.10.10.3
netbios-node-type h-node
default-router 10.0.22.20
lease 3
!
interface Ethernet0/0
ip address 10.0.22.20 255.255.255.0
full-duplex

!
ip classless
ip route 0.0.0.0 0.0.0.0 Ethernet0/0
no ip http server
!
!
line con 0
line aux 0
line vty 0 4
login
!
end

 

[jneiberger]

If your laptop is on the 10.0.22.0/24 network then I'd suspect that you're running firewall software that is blocking ICMP.

 

[Motopsycho]

Nope..no firewall blocking ICMP.

 

[jneiberger]

Are you absolutely certain that your laptop is using an address from the 10.0.22.0/24 network, and that the subnet mask is correct?

 

[Motopsycho]

Yes positive. In fact, the router assigns the IP address from its DHCP pool as shown in the config above.

 

[jneiberger]

I can't think of anything else that would cause this behavior. I hate to beat a dead horse, but is your laptop a Windows machine? If so, are you sure that the Windows firewall didn't get turned on somehow?

If you have layer two connectivity and your layer three config is correct, access lists or firewalls are about the only other thing I can think of that would block ICMP.

 

[Motopsycho]

It is a Windows machine and I use it everyday for network diagnostics. I've reviewed everything and can't figure out why it doesn't ping. Interface is up/up, duplex/speed match, same subnet...I even tried turning off DHCP and manually assigned an IP to my PC using the same subnet and mask. Same thing! I tried 3 different cables and 3 different routers with the same result. If I ping the router ethernet interface from within the router via a console cable, it replies no problem. If someone has a router available, try it out and see if you can replicate this. The only thing that I can think of is that some kind of routing loop is occuring.

 

[jneiberger]

You shouldn't have a routing loop because no routing is occuring, really. All traffic in this scenario should be local to the subnet. You could disable IP routing on the router and this should still work with no problem.

If you do a "show arp" from the router, do you see a complete entry for the IP address of your laptop?

 

[Motopsycho]

I am running into the same issue with another router..this time a 2620 with a similar config. DHCP hands out the IP but I am unable to ping the router ethernet interface and vice-versa. A sho arp on the router shows my laptop IP and MAC address. I can't understand this behavior.

 

[vipergg]

Did you try running the connection at half duplex and see if the results are any different . Seems to me even though the full duplex command was sometimes there it really couldn't run full duplex , try half on both ends though that wouldn't account for the arp table entries , would also check for anything funky in the host table on the pc...