Solved: Ping only works on extended ping with different vlan

Zahan Al-Rashid · ‎08-22-2012

Hi all,

My ping works using extended vlans but not when I ping from the switch (ip 192.168.77.129)

3750#ping

Protocol [ip]:

Target IP address: 192.168.2.16

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands [n]: y

Source address or interface: vlan 888

Type of service [0]:

Set DF bit in IP header? [no]:

Validate reply data? [no]:

Data pattern [0xABCD]:

Loose, Strict, Record, Timestamp, Verbose[none]:

Sweep range of sizes [n]:

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.2.16, timeout is 2 seconds:

Packet sent with a source address of 192.168.81.1

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/8 ms

Now clearly the routing to and from source to destination device is correct for this ping to work from the switch so why not for 192.168.77.129? Please advise.

Alessio Andreoli · ‎08-22-2012

Hi Zahan,

to verify connectivity you should use:

ping 192.168.2.16 source vlan 888

and the same test with other IP addresses. I would say you should understand with which source IP the ICMP is encapsulated and checking if this IP is properly routed. In this case, when in your extended ping you specify vlan 888 the source address will be the ip address you stated in

int vlan 888

ip address 192.168.81.1 255.255.255.0

If you understand which ip address the switch use as source ip address when you do NOT specify anithing (like vlan 888) you can easily find out your issue

Take Care

Alessio

View solution in original post

Alessio Andreoli · ‎08-22-2012

Hi Zahan,

to verify connectivity you should use:

ping 192.168.2.16 source vlan 888

and the same test with other IP addresses. I would say you should understand with which source IP the ICMP is encapsulated and checking if this IP is properly routed. In this case, when in your extended ping you specify vlan 888 the source address will be the ip address you stated in

int vlan 888

ip address 192.168.81.1 255.255.255.0

If you understand which ip address the switch use as source ip address when you do NOT specify anithing (like vlan 888) you can easily find out your issue

Take Care

Alessio

Zahan Al-Rashid · ‎08-22-2012

Thanks for your response.

Your right, if I specify the source address as 192.168.77.129 ping also works. so it appears that this address was not being used to ping by default. is there anyway to know which IP address the switch assumes when pinging?

thanks for your assist.

Alessio Andreoli · ‎08-22-2012

Difficult question

I would issue

show cdp nei det

from a cisco device directly connected!!!

Take Care

Alessio

cadet alain · ‎08-22-2012

Hi,

sh ip route x.x.x.x and recursion will tell you which address is used if there ain't no PBR overriding the routing behaviour.

Regards.

Alain

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