What should the duplex mode to be set on a routed port gi0/21 that are running HSRP ? I try setting the gi0/21 to full, but it caused the port to be down.
The only way for the port to be up is setting it to half duplex. Please advise..
Cisco 3750 Switch
ip address 10.200.104.34 255.255.255.248
standby 3 ip 10.200.104.33
standby 3 priority 105
standby 3 preempt
%CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on GigabitEthernet0/21 (not full duplex), with CO2CAT26 FastEthernet0/11 (full duplex).
GigabitEthernet0/21 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is 64ae.0c3e.b545 (bia 64ae.0c3e.b545)
Description: Starhub OAM uplink
Internet address is 10.200.104.34/29
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Half-duplex, 100Mb/s, media type is 10/100/1000BaseTX
duplex setting has nothing to do with HSRP.
It just needs to be the same on both devices which are connected physically.
100 Mbps/HalfDuplex is usually a result of port autonegotiation failed.
According to your logg message it looks like your Cisco 3750 Switch interface GigabitEthernet0/21 is connected to the switch CO2CAT26 FastEthernet0/11 interface which has full duplex configured.
If that's really true you should configure full duplex on your port, too.
But check the physical cable connnection.
It's possible in theory there might be some other device between those two Cisco devices (hub, non-Cisco switch) which might forward CDP frames causing a confusion...
When the Gig interface was going down I am guessing that you did not hard code the speed and duplex, rather just let it auto negotiate. Have you tried to configure both interface for full/100?