I am having 2960 switch and one port is configured with a VLAN and connected with an unmanageable switch and further one more unmanageable switch was connected to the primary unmanageable switch…
The topology will be 2960 switch -> unmanageable Switch -> unmanageable -> PC connected
The issue I am facing most of the PC are getting IP addresses through DHCP server and very few 5 or 6 PC’s out are not getting the IP from DHCP server.
If I switch of the switch and switch on the issue is resolved for those and it will raise for some other PC’s.
Thanks you team......
What do you mean by, "If I switch of the switch and switch on the issue is resolved for those and it will raise for some other PC’s".
Sorry in delay,
Switch of means Switch "power OFF" and Switch on means Switch "power ON"
Thanks for the responce........
Waiting fo the reply.....
Is dhcp server connected to 2960 switch?
Have you try to connect all dhcp clients to 2960 switch to eliminate the problem with unmannaged switches (if possible at all)?
Have you enabled any security features on 2960 (port security, dhcp snooping..)?
I'm almost sure the problem is not lying in exhausted dhcp address pool but verity that just in case.
Check the security on the 2960 switch port...show port-security interface fa0/1... It might be configured in a way that allows a certain number of MAC addresses to be connected.
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Can you show us the show runn of the interface on 3750 that connects to 2960 and same on the 2960 that connects to 3750. Also the show runn of the interface that connects to the unmangeable switch. I'm going to assume this is a windows based DHCP server so did you look at the error log on it?
does it looks like this:
core switch---->2960---> unmanagable switch---->computers and un managable switch or only unmanagable switch----> computers.
If the scenario is
core switch---->2960---> unmanagable switch---->computers and un managable switch----> computers
Is the problem lying at this first unmanagble area or second or both.
Change the switch where the problem is lying.
If the scenario is
core switch---->2960---> unmanagable switch---->un managable switch---->computers
Change the Last unmanagble switch first and check the status.
If some PCs are getting the dhcp ips and some other are not getting then there might be the issue.
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Posting part of the config would be helpful, but I'll offer this up being I've seen some weirdness in the past like this. On your cable run from each switch, ensure you are using the appropriate cable type IE crossover cable. Yes, many newer switches of all types employ Auto MDIX on them, but quite frankly don't rely or use it on those runs from switch to switch. You're only asking for trouble IMO. Also, ensure you hard set your speed and duplex type on your 2960 to ensure you don't have any weirdness occur. So on your port that runs from your 2960 to your first unmanaged switch I would add these commands after ensuring you have crossover cables running from switch to switch to switch.
no mdix auto
speed 100 (that assumes it is a 100 mbps link)
duplex full (that assumes it is a full duplex switch)
Then power cycle your 2960 (I believe the MDIX command won't take effect until you power it down and repower it).