orus
asked on
Cannot pull dhcp ip switchport problem?
I have a 2960 connected with 1gb copper to our 4507 core. Recently, we've noticed we cannot pull ip addresses from some of the switch ports, via DHCP. Specifically ports 1-3
What would be the cause of this? There are 161 total mac addresses in the cam table. Several of them are learned via the uplink to the core. I have over 8000 mac entires free, so I don't think my CAM table is full
We have an IP phone which can plug into the mentioned switchports, and pull an IP via DHCP no problem. PCs cannot pull an IP if plugged directly into the switchports. However, if plugged into the back of the avaya phone, they can pull an ip
These switchports were also trunk links, with a default vlan in the data network. I changed some to a regular access port, and the pcs still could not pull an IP
What would be the cause of this? There are 161 total mac addresses in the cam table. Several of them are learned via the uplink to the core. I have over 8000 mac entires free, so I don't think my CAM table is full
We have an IP phone which can plug into the mentioned switchports, and pull an IP via DHCP no problem. PCs cannot pull an IP if plugged directly into the switchports. However, if plugged into the back of the avaya phone, they can pull an ip
These switchports were also trunk links, with a default vlan in the data network. I changed some to a regular access port, and the pcs still could not pull an IP
Ports 1-3 need to be assigned to a specific VLAN, one which either has a DHCP server on it or for which BOOTP helpers have been created. Even though they are no longer trunk ports, you need to either assign them to a VLAN or they will default to Native VLAN (VLAN1).
ASKER
yes they are part of vlan 14 (data)
Is the rest of the switch on VLAN14? Are you able to post an Interface config?
Is Spanning-Tree enabled? When you plug a device into the port, how long before the LED turns green?
ASKER
here are ports 1-3. I'm having the issue on other ports as well. Ip-phone works, but pcs cant pull anything plugged directly in
interface GigabitEthernet1/0/1
switchport access vlan 14
srr-queue bandwidth share 10 10 60 20
queue-set 2
priority-queue out
mls qos trust dscp
auto qos voip trust
!
interface GigabitEthernet1/0/2
switchport trunk native vlan 10
switchport mode trunk
srr-queue bandwidth share 10 10 60 20
queue-set 2
priority-queue out
mls qos trust dscp
auto qos voip trust
!
interface GigabitEthernet1/0/3
description ***IT WAP***
switchport mode trunk
srr-queue bandwidth share 10 10 60 20
queue-set 2
priority-queue out
mls qos trust dscp
auto qos voip trust
!
ASKER
yep, STP is enabled. Also, other ports are fully functional. It is strange indeed
ASKER CERTIFIED SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
ASKER
DHCP server is on a different switch, going through gig1/0/48. It is on a different VLAN, VLAN 1. yes there is a trunk port to carry VLAN14
#3 is an AP and it is working yes
#3 is an AP and it is working yes
DHCP on VLAN 1.
Client on VLAN14.
They can PING each other if they use static IP addresses.
Is there anything else on VLAN14?
It really sounds like BOOTP helper is not configured for VLAN14. Because DHCP requests are broadcast, it needs the router to forward DHCP requests from VLAN14 to VLAN1.
On the router, interface VLAN14, do you have a command that is similar to "ip helper-address <dhcp>"? You need one...
Client on VLAN14.
They can PING each other if they use static IP addresses.
Is there anything else on VLAN14?
It really sounds like BOOTP helper is not configured for VLAN14. Because DHCP requests are broadcast, it needs the router to forward DHCP requests from VLAN14 to VLAN1.
On the router, interface VLAN14, do you have a command that is similar to "ip helper-address <dhcp>"? You need one...
ASKER
we have had it on there a while actually. This is from the core switch. Do we need the ip helper command on the access switch as well
interface Vlan14
description ***IT Personnel VLAN***
ip address 172.16.14.1 255.255.255.0
ip helper-address 172.16.1.14
interface Vlan14
description ***IT Personnel VLAN***
ip address 172.16.14.1 255.255.255.0
ip helper-address 172.16.1.14
This command looks good and should be issued on the router only. And of course, the DHCP server has 172.16.1.1 as it's default gateway? And the client and DHCP server can PING if using static?
ASKER
i will try static and report back
Were you able to test ping to ensure connectivity between VLANs?