Layer 2 Problem

[smavashev]

The weirderst Problem of all

2950 Switch is Connected to 3550 connected to 2801 Router

2950 Mangement IP to VLAN 1 192.168.1.103

2950 Default Gateway   192.168.1.1

PC1 = 192.168.20.2

MASK = 255.255.255.0

DEFAULT G - 192.168.20.1

PC2= 192.168.20.3

MASK = 255.255.255.0

DEFAULT G - 192.168.20.1

3550

SVI = 192.168.20.1

has IP helper-address to 2801 of 10.1.1.1

PC1 is ping all the way to 2801, PC2 I can't even ping from PC1, I'm confused because at Layer 2 on the same subnet PC1 at least should be pinging PC2, it was working fine yesterday but I can't figure it out. HELP !!!

[singhaam007]

Hi Sergei,

If you cannot ping the other computer from a computer on the same subnet, ensure that the other computer is connected to the network and that you have the correct IP address for the other computer. check if there is any cableing issue.

ping loopback address to see if TCP/IP working on machine

more likely its layer one issue.

check arp table.

just to add

do this, on the switch do a "show interface XXX" and see if it says up/up, up/down or down/down that will tell you where to start at.

thanks

[smavashev]

I cleared the arp cache with the command  netsh interface ip delete arpcache

I pinged LoopBacks on both PC1 and PC2 and getting fine reply's..

I checked the cables and all lights are on.

I pinged from PC1 (192.168.20.2) to PC2(192.168.20.3) working fine

I pinged from PC1 (192.168.20.2) to PC2(192.168.20.3) and getting request time out.

Both PC's are on VLAN 20, all ports are added to VLAN 20 from Layer2 Switches.

I also think it's an arp problem, but I'm not sure how to troubleshoot.

[smavashev]

Sep 21, 2012 3:29 PM                             (in response to Amrinder Singh)

Layer 2 Problem

I cleared the arp cache with the command  netsh interface ip delete arpcache

I pinged LoopBacks on both PC1 and PC2 and getting fine reply's..

I checked the cables and all lights are on.

I pinged from PC1 (192.168.20.2) to PC2(192.168.20.3) working fine

I pinged from PC1 (192.168.20.3) to PC2(192.168.20.2) and getting request time out.

Both PC's are on VLAN 20, all ports are added to VLAN 20 from Layer2 Switches.

I also think it's an arp problem, but I'm not sure how to troubleshoot.

[singhaam007]

check windows firewall on 192.168.20.3 .

A firewall that blocks ICMP would typically allow ICMP replies from pings, but not pings that it did not initiate

turn it off aand try

thanks

[Aref Alsouqi]

Try to ping its default gateway 192.168.20.1 to verify that the issue is on pc2 or on the switch.

One more test you can do is to bypass the switch by connecting the two pcs pc1 and pc2 directly together and see if the issue is persist, in this case, the issue is on pc, so you have to check the windows firewall "as it was already suggestef" and if you have any security software on the pc that might block the return icmp traffic to the pc.

In case ping worked with the direct connection, so you can test the issue on the switch by cheking that the interface is up "no shut" note that if the int is in err-disable you have to shut it down first then no shut it down to bring it in up.

You can too, creat an acl on the switch of the traffic from and to that pc and see at least if there are any hits on it.

Hope being helpful.

Aref

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[smavashev]

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