Is Ethernet a protocol?

Cisco router 2651XM fast ethernet port always 'line protocol down'?

• I am setting up a WLAN using a 2950 switch and as stated above a 2651XM. The access point will broadcast multiple SSID's mapped to different VLAN's. It wasn't working and I managed to discover my problem is that no matter what I configure the fast ethernet to do it just will not turn the port to 'line protocol down', when I do a show int fa0/1. I recently upgraded the firmware to 'c2600-ik9s-mz.123-22.bin' with no problems. All the cables are working and are the correct cables, i.e. straight through. The WLAN is going to be set up on as a router on a stick. If anyone could help me with this I would really apprepriate the help with this as it has me baffled to be honest.

• Answer:

  There are only 3 things that will cause this problem: 1. Ports misconfigured. There are two parts here. a. The Ethernet port on the router and the one that it's connected to on the switch must be configured the same way, i.e same speed and duplex setting or both set to auto. Cisco equipment is notorious for not liking up if one end is configured for auto speed and duplex and the other end is manually configured to any speed and duplex setting. b. The next part of port misconfiguration is the VLAN configuration. The switch port for a router-on-a-stick needs to be set up for trunking. For example if you're using interface fa0/0 on the switch to connect the router: SW0# configure terminal SW0(config)#int fa0/0 SW0(config­if)#switchport trunk encapsu…‡ (should say encapsulation dot1q) SW0(config­if)#switchport mode trunk SW0(config­if)#^Z Then on the router's fa0/1 you must set up subinterfaces for the VLANs after you configure the VLANs on the router. Remember, the ingress and egress ports can't be the same for any packet, so subinterfaces are mandatory. For example: R0# configure terminal R0(config­if)# R0(config­if)#int fa0/0.10 R0(config­subif)#encapsulation dot1q 10 R0(config­subif)#ip address 192.168.1.1…‡ (should have the IP address and subnet mask) R0(config­subif)# R0(config­subif)#int fa0/0.20 R0(config­subif)#encapsulation dot1q 20 R0(config­subif)#ip address 192.168.2.1…‡ (should have the IP address and subnet mask) R0(config­subif)# R0(config­subif)#^Z 2. Bad or incorrect cable. Be sure that the cable is truly a straight through cable and is set up to the 568B standard at both ends. Lines 1 and 2 on the same twisted pair (usually orange) and 3 and 6 on the same twisted pair (usually green). 4 and 5 should be on the blue pair and 7 and 8 on the brown pair. Split pairs may sometimes work at 10 mbps but won't at 100 mbps or greater. 3. Dead port. If it's not 1 or 2, this is your problem. Well, OK there is a 4th cause -- port shutdown -- but I'll assume that you already checked that. Edit: Arrgh! Y!A is truncating some of my entries. Here's a link to a guide that should help: https://learningnetwork.cisco.com/servlet/JiveServlet/download/5507-2434/Router%20on%20a%20Stick.pdf