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.
