05-25-2007 09:53 AM - edited 03-03-2019 05:09 PM
I am connecting a Cisco router to a Cisco MLS. The router interface is fastE, in full-duplex mode. The MLS interface is GigE, in 100Mbps, full-duplex mode. The link on the router fastE came up, but the link on the MLS gigE link is down. Is there something else I should configure?
Both sides are using vlan.
05-25-2007 10:17 AM
Hi Sarah
Could you please tell whether u have force the command speed 100 on the MLS. and on router its set to auto.
regards
Mukesh
05-25-2007 10:32 AM
Yes, the MLS interface is 10/100/1000, and I forced it to 100Mbps.
The router interface is fastE.
MLS config:
interface GigabitEthernet2/11
switchport
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 12
switchport mode trunk
no ip address
load-interval 30
speed 100
duplex full
mls qos trust dscp
storm-control broadcast level 30.00
end
interface Vlan12
ip address ... ...
ip ospf network point-to-point
ip ospf hello-interval 1
ip ospf dead-interval 3
load-interval 30
service-policy output monitor_traffic
end
Router config:
interface FastEthernet4/1/0
no ip address
load-interval 30
full-duplex
end
interface FastEthernet4/1/0.12
encapsulation dot1Q 12
ip address ... ...
ip ospf network point-to-point
ip ospf hello-interval 1
ip ospf dead-interval 3
no snmp trap link-status
end
The strange thing is, the interface on the router is up up, but the interface on the MLS is down down.
If I bounce the interface on the MLS, I see the interface on the router goes down, so they are connected correctly.
05-25-2007 10:50 AM
Hi Sarah,
set the MLS side also to auto and router is alreasdy auto this way the MLS switch and router will autonegotiate the link speed.
regards
Mukesh
05-25-2007 10:55 AM
Inadvisable.
10/100 Ethernet standard has no duplex negotiation built into it.
Gigabit, however, does.
05-25-2007 11:03 AM
I configured both sides to be auto/auto, and both links are down. :-( Bounced both interfaces, and still no help. :'(
Maybe 10/100/1000 interface doesn't work well with GigE interface.
05-25-2007 11:01 AM
How is it that the router has allowed you to configure duplex without first hard-setting speed? Most Cisco routers will balk at attempting this.
Try adding VLAN1 to the allowed VLANs on the MLS port. VLAN1 is typically the default native VLAN for dot1Q tagging unless you have specified elsewhere in your config.
05-25-2007 11:17 AM
For GigE interfaces, you have to configure speed to non-auto before configuring duplex mode. For FastE interfaces, you don't have to, since the speed is not configurable. The interface on the router is FastE.
05-25-2007 11:24 AM
Speed is configurable on FastEthernet interfaces as it is typically capable of running 10/100 unless it is a fiber link.
05-25-2007 11:17 AM
You're also missing your native VLAN on your router...
int FE4/1/0.1
Description Native Dot1Q VLAN
Encapsulation dot1q 1 native
no ip address
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