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New Member

Bizarre routing issue

I have a 6509-E switch acting as our core router on campus. It has dual 720Sups running IOS Version 12.2(33)SXI11.

In the past few weeks, I have been having a few (approximately 5-10%) of my clients on various VLANS having issues where they get perfectly valid IPs within the legal range of their subnet, with valid gateways, and all other information received from DHCP as appropriate, yet they are unable to talk to anything outside their subnet.

It seems to be completely random.  For example, I have one in front of me now from VLAN 136:

interface Vlan136

description administration

ip address XXX.XXX.136.1 255.255.248.0

ip access-group fromAdmin in

ip access-group toAdmin out

ip helper-address XXX.XXX.2.48

ip helper-address XXX.XXX.2.50

no ip redirects

no ip unreachables

ip pim sparse-dense-mode

ip flow ingress

end

and it has the following info:

IP     XXX.XXX.137.163

SN     255.255.248.0

GW:     XXX.XXX.136.1

Now, if I change my dhcp host management to give this system a different IP, it will work perfectly.

Also, if I take this IP information and hard code it on another device, THAT works perfectly.

It does not appear to be a problem with either the client OR the ip address, just a combination of the two.

From the affected client, I can ping XXX.XXX.136.1, but I cannot ping the DNS server, living on another subnet, nor can I ping the dhcp servers (specified in the helper-address statements).  I can ping all those things from an unaffected system living on the same subnet as the affected system.

I can only assume that the problem lies at the 6509-E, as the problem affects people on wired subnets and also people who are connected via Wireless to our WLC5508 controlled wireless network (on subnets unique to that wireless network).

Any ideas?  Let me know what other information might be required to help diagnose this.

Everyone's tags (5)
2 REPLIES
New Member

Bizarre routing issue

As a test, I just tried hardcoding the MAC address from the affected end point to another laptop and disconnected the affected system and I plugged the new test system into the exact same edge port as the affected system.

Upon obtaining the same IP on the new system via DHCP, I was fully connected with no issues.

I then shut that system down, and plugged the previous affected system back in. It got the same IP address and now was able to ping anywhere and all was working.

Unfortunately, now I am unable to further test if the problem is resolved, as my previously affected system is now mysteriously working.

One thing I do notice:  My dual 720sups BOTH have "minor errors" in the diag results:

  5  Minor Error

  6  Minor Error

The active one has a failure at:

   15) TestMPLSFibShortcut -------------> F

The hot standby has a failure at:

   41) TestCFRW:

      Device  1  2

      ------------

              F  U

I have no idea what these failures indicate and if they may be the cause of this outage.  Any help?

New Member

Bizarre routing issue

Turned out to be a Faulty 720Sup.  RMAd. Resolved.

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