Interface Information... confusion..

Answered Question
May 18th, 2007

Hi, just a little confusion..

when i run the comand "show ip interface brief"

i get the output ..

Router#sh ip int brief

Interface IP-Address OK? Method Status Proocol

FastEthernet0/0 92.168.26.251 YES NVRAM up down

FastEthernet0/1 192.168.4.254 YES NVRAM up up

now the funny thing is that i done have any cable connected to the interface Fe0/0

shouldnt the status be showing "down" ???

cause if i shut it don then it shows administratively shutdown.. i theres a cable connected to it then status shows up..

any help.. ?

the router is 2801 with IOS version 12.4

I have this problem too.
0 votes
Correct Answer by royalblues about 9 years 6 months ago

Friend,

The fast ethernet interface will never show the interface as down after you do a no shut to the interface.

It does not rely on any carrier detects as in serial interfaces and hence displays this behavior. This is independent of the platform and not specific to 2801

HTH, rate if it does

Narayan

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ankbhasi Fri, 05/18/2007 - 02:31

Hi Shaukat,

Can you paste the output of "sh run int fa0/0" and "sh run int fa0/1" ?

Regards,

Ankur

Correct Answer
royalblues Fri, 05/18/2007 - 02:41

Friend,

The fast ethernet interface will never show the interface as down after you do a no shut to the interface.

It does not rely on any carrier detects as in serial interfaces and hence displays this behavior. This is independent of the platform and not specific to 2801

HTH, rate if it does

Narayan

ankbhasi Fri, 05/18/2007 - 03:08

Hi Shaukat,

I believe Narayn explained you the reason. I did not read your question completely and thaught you are asking fa1/1 is up and up without anything connected and that is the reason I asked the outputs. You can ignore my post.

What you are observing is expected behavior.

Regards,

Ankur

mohammedmahmoud Fri, 05/18/2007 - 03:18

Hi,

Narayan has explained it perfectly, only one thing to add, always make sure that keepalives is set under the Ethernet interface, in order to reflect the real state of the interface.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

a.shaukat Fri, 05/18/2007 - 05:08

So u mean to say that the FastEthernet interfaces will never show its status as down unless the interface is shutdown administratively. ??????

meaning that these interfaces (when no shut) will always be up regardless if any cable is inerted into it or not...

is there any cisco's word on this regards ?? cause im having a point of conflict with an ISP's tech support...

thanks for the support..

heres my interfaces info too...

Router#sh ip int fastEthernet 0/0

FastEthernet0/0 is up, line protocol is down

Internet address is 192.168.26.251/24

Broadcast address is 255.255.255.255

Address determined by non-volatile memory

MTU is 1500 bytes

Helper address is not set

Directed broadcast forwarding is disabled

Multicast reserved groups joined: 224.0.0.9

Outgoing access list is not set

Inbound access list is not set

Proxy ARP is enabled

Local Proxy ARP is disabled

Security level is default

Split horizon is enabled

ICMP redirects are always sent

ICMP unreachables are always sent

ICMP mask replies are never sent

IP fast switching is enabled

IP fast switching on the same interface is disabled

IP Flow switching is enabled

IP CEF switching is enabled

IP CEF Flow Fast switching turbo vector

IP multicast fast switching is enabled

IP multicast distributed fast switching is disabled

IP route-cache flags are Fast, Flow cache, CEF, Full Flow

Router Discovery is disabled

IP output packet accounting is disabled

IP access violation accounting is disabled

TCP/IP header compression is disabled

RTP/IP header compression is disabled

Policy routing is disabled

Network address translation is disabled

BGP Policy Mapping is disabled

WCCP Redirect outbound is disabled

WCCP Redirect inbound is disabled

WCCP Redirect exclude is disabled

royalblues Fri, 05/18/2007 - 05:16

Yes,

FastEthernet interfaces will never show its interface status as down after a no shut.

The line protocol will be down if for eg there is mismatch in the cable cross vs straight

I could not find a document regarding the same in CCO

HTH, rate if it does

Narayan

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