Questions tagged [cisco-commands]

Used for questions about the commands for Cisco devices.

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24 answers
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How can I see which switchports are not in use?

On a large Cisco Catalyst switch stack, almost all switchports are patched. I need to identify the ports, which are not in use, for connecting further devices. Following switchports, cabling, patch ...
Stefan's user avatar
  • 3,374
25 votes
5 answers
29k views

Accidentally Removed Allowed VLANs from Cisco Switch Dot1Q Trunk

I am adding a new VLAN to an existing trunk port between two Cisco Catalyst switches (3750's). In the process of adding the new VLAN, it appears that I've removed the existing allowed VLANs on the ...
Brett Lykins's user avatar
  • 8,278
18 votes
2 answers
37k views

Cisco - display ALL routes using a single command

In Junos when you use a show route it displays the routing tables , starting with inet.0 ( global routing table) and then listing each VRF in alphabetic order. I am after a similar command , for the ...
DrBru's user avatar
  • 1,619
16 votes
5 answers
239k views

How can I reset a VPN tunnel on a Cisco ASA?

On a site-to-site VPN using a ASA 5520 and 5540, respectively, I noticed that from time to time traffic doesn't pass any more, sometimes just there's even missing traffic just for one specific traffic ...
Stefan's user avatar
  • 3,374
16 votes
3 answers
71k views

What does logging synchronous command do?

Can somebody describe me what does logging synchronous command do ?
Abiral's user avatar
  • 489
14 votes
1 answer
2k views

BGP "no synchronization" command not showing up in running-config

I noticed in the running config I don't see the no synchronization command under the BGP section. Is this a default command so I won't see it unless I change it? Hardware / software Cisco 1921 c1900-...
evolvd's user avatar
  • 754
11 votes
11 answers
4k views

Locate a host on Network

What is the best method of locating a particular workstation on a VLAN ? I sometimes need to do this, if a workstation IP address, shows up on an ACL Deny torrent use High bandwidth usage (Top ...
hyussuf's user avatar
  • 467
10 votes
5 answers
3k views

How can I speed up CLI typing in Cisco IOS using shortcuts?

I know we can use auto-completion (tab key) and abbreviated commands (such as sh ip int bri) to speed up typing. However, I'm still not satisfied with typing crypting chains such as sh ip dh sn bi | ...
Stefan's user avatar
  • 3,374
10 votes
3 answers
15k views

Cisco: prevent vlan's of communicating with eachother on cisco router (ACL alternative)

Setup: Cisco router with multiple VLAN's configured on it. How can you prevent 2 VLAN's communicating with eachother? Normally I would do this with ACL's like this: access-list 102 deny ip 1.1.1.0 0....
Bulki's user avatar
  • 2,383
10 votes
1 answer
380 views

Deconfigure an interface in IOS with one command

I was wondering if there is a single command to clear a single network port's configuration? (wipe switchport, portsecurity,...)
Lucas Kauffman's user avatar
10 votes
2 answers
4k views

How can I disable SIP on IOS 12.x

How would I disable SIP on an Cisco router running IOS 12.x?
Ryan's user avatar
  • 103
10 votes
1 answer
5k views

Cisco IOS: Show ip route output order

I am runing some BGP tests through the lab before rolling them out in production (thus, any IP addresses or AS numbers etc used here are done so in a completely fictitious manner). Something that has ...
Baldrick's user avatar
  • 5,300
10 votes
2 answers
3k views

What do these three options in a Cisco Router NAT configuration mean?

In a standard Static PAT configuration, where one IP:Port combination is always mapped to another IP:Port combination, there are three possible combinations of inside/outside/source/destination that ...
Eddie's user avatar
  • 15k
10 votes
1 answer
2k views

QoS between two VLANs with Cisco 881 Router (IOS)

I'm hoping to get some advice regarding the best practice to delegate a limited Internet connection between two VLANs. In my case, one VLAN is for an office network, and the other is for guests. What ...
David Rediger's user avatar
10 votes
1 answer
20k views

Cisco config example for Policy Based Routing

I find my self in a situation I was in not too long ago, but I can't remember how I resolved it :) The Scenario I have a Cisco IOS router with a LAN interface (fa0/0) and a WAN interface (fa0/1), ...
Baldrick's user avatar
  • 5,300
10 votes
1 answer
5k views

PPPoA ADSL Configuration with external modem on Cisco 891

Context We use Cisco 891 routers as CPE for several client sites. They are all running IOS 15. Cisco IOS Software, C890 Software (C890-UNIVERSALK9-M), Version 15.0(1)M8, RELEASE SOFTWARE (fc1) The ...
Geekman's user avatar
  • 1,478
9 votes
5 answers
10k views

Monitor specific traffic type on a Cisco router

Is it possible to monitor a specific traffic type going through a cisco router? (like monitoring via wireshark) Ex: I want to monitor http traffic specifically that is passing through a router. (or ...
Bulki's user avatar
  • 2,383
9 votes
1 answer
57k views

Diffrence between "wr" and "copy running config to startup config"

For saving configuration in Cisco devices we have "wr" and "copy running config to startup config" i am curious what is difference between these two command.
R1w's user avatar
  • 311
9 votes
3 answers
714 views

Why does "show adjacency" take so long to run?

Why does the "show adjacency" command take so long to run (in the order of minutes) on Cisco IOS Software, 7200 Software (C7200P-SPSERVICESK9-M), Version 12.4(4)XD5, RELEASE SOFTWARE (fc1)? The ...
generalnetworkerror's user avatar
8 votes
1 answer
7k views

About the inside local and outside local and inside global and outside global

I have some concept problem with the NAT. Here is the Cisco definition for the local and Global and the NAT operation. Local address—A local address is any address that appears on the inside ...
Samuel's user avatar
  • 369
7 votes
5 answers
4k views

Why does the Cisco show run command not show the full version, while the show version command does?

Is there any reason why Cisco show run does not show the full version which is 16.3.7 in this example? IOSSW#show running-config | include ersion version 16.3 while show version does? IOSSW#show ...
user11392987's user avatar
7 votes
2 answers
3k views

What is the difference between "ip domain name" and "ip domain-name"?

I'm running a ISR 4221 with "Cisco IOS XE Software, Version 16.04.02". I see that it has both ip domain name and ip domain-name commands. Why? Is this some sort of compatibility thing? My 7206 ...
Erik Bennett's user avatar
7 votes
2 answers
3k views

Configuring redundancy using floating static

I wanted to post my network layout, but I dont have the required reputation. So I have made up a network diagram below: ISP / \ / \ / \ HQ------Branch | ...
bob's user avatar
  • 71
7 votes
2 answers
5k views

"transport input" for AUX port in Cisco routers

On physical layer AUX port works on asynchronous serial RS-232 protocol. However, one can specify various application layer protocols like telnet or SSH as allowed input protocols under AUX line ...
Martin's user avatar
  • 1,229
7 votes
2 answers
3k views

"Local Policy Denied Prefixes" in 'show ip bgp neighbor' output

I've been spending the last week or so troubleshooting some (maybe related, but probably not) issues with Quagga. I have a test router - 7204VXR-NPEG2 running 12.4(24)T6 - with a single BGP session to ...
John Jensen's user avatar
  • 9,037
6 votes
2 answers
40k views

What does no shutdown command do? Cisco

Newbie here. I'm studying networking and struggling to understand the no shutdown command. I don't understand what no shutdown command actually does. I've read that it enables the interface but I don'...
The_Bear's user avatar
  • 515
6 votes
2 answers
4k views

SNMP and Syslog in configuration

Really stupid questions guys so I apologize. When sending Syslog messages to a server we use the command logging x.x.x.x. I get that part. SNMP is used to gather stats or change configurations on ...
Michael Moore's user avatar
6 votes
2 answers
6k views

Cisco show log number of messages

When I run the "show log" command, it displays the latest 360 messages. Why 360? Can this value by changed? If yes, what is the command for that? Thanks.
Léa Massiot's user avatar
6 votes
4 answers
24k views

Reconfiguring Layer3 Switch to enable IP routing and become the default gateway

Current configuration with HP Procurve 2848 switch at a colocation facility consists of using the ISP switchport as the default gateway. The current configuration is very basic with only 1 vlan assign ...
Damainman's user avatar
  • 171
6 votes
2 answers
17k views

VLAN Interface is down, protocol is down

I have Cisco Layer 3 switch with IP routing enabled on it. I have different VLANs configured on it and its working perfectly. Now i have added another VLAN (SVI) and assigned that VLAN to one of the ...
Junaid's user avatar
  • 163
6 votes
2 answers
2k views

Why is Cisco enforcing X:X:X:X::X for link-local addresses when the standard says FE80:/10?

This document shows that you can use one of these options: interface type/number ipv6 address ipv6-prefix/prefix-length eui-64 ipv6 address ipv6-prefix/prefix-length link-local <------...
MiniMe's user avatar
  • 415
6 votes
2 answers
61k views

Show connected (up) interfaces on cisco devices

Is there any way to show a total count of interfaces that are in status "up" on a cisco router? The purpose is to let a script go through all routers and show a summarization count of "up" interfaces....
Bulki's user avatar
  • 2,383
6 votes
1 answer
3k views

How do I create an SSL CSR via CLI for Cisco Prime?

I'm trying to create a csr for a cisco prime server. I managed to create a csr and put it in the "defaultRepo", which is local on the disk. After what I've read I need to create a certificate repo ...
Garmroth's user avatar
6 votes
1 answer
6k views

Chassis temperature and Fan status on Cisco 3548 switch

I need to remotely check the status of the fans and temperature of a switch that I currently do not have physical access to. I have done so in the past on a 2950 with the command: Show environment ...
GerryEgan's user avatar
  • 661
6 votes
1 answer
3k views

Cisco 867 forward UDP port range

I need to forward an UDP port range to a specific private IP address in my LAN. In order to forward one port to an internal IP I do: access-list <acc_list_number> permit <port_type> any ...
eldblz's user avatar
  • 206
6 votes
2 answers
4k views

SNMPv3 Setup - Cisco 3750

I am not a network guru by any means but need to setup our router/switch to use SNMPv3. I am installing What's Up Gold on our system and configured the settings (changed for this post) as follows: ...
JMeterX's user avatar
  • 163
5 votes
3 answers
58k views

How IP helper address works?

How IP helper address works and what is the difference between dhcp and IP helper-address .please explain in brief.
Harsha D's user avatar
5 votes
1 answer
5k views

How to Disable telnet on Cisco switch totaly?

I have disabled telnet on Cisco 2960G switch by putting: line vty 04 transport input ssh but now when I try telnet to the switch I get message saying,password required but not set I am wondering ...
Mr.lock's user avatar
  • 1,723
5 votes
2 answers
1k views

spanning tree RootGuard question on vPC switches

I have following diagram and two distribution switch connected back to back over vPC Related spanning-tree question is it ok to use RootGuard on both distribution switch where access switch is ...
Satish's user avatar
  • 4,379
5 votes
2 answers
6k views

Cisco: No autostate on GigabitEthernet interfaces, any alternative? (not working)

I recently tried the command "no autostate" on a GigabitEthernet interface (on a newer router) and this didn't work anymore, does anyone know why this is occuring? This use to work on FastEthernet ...
Bulki's user avatar
  • 2,383
5 votes
1 answer
13k views

time based interface shutdown on cisco router

Is there a way to shutdown an interface on a Cisco router based on time periods? I would like to shut the cellular interface when it is not necessary. Can this be done with the event manager and ...
smignon's user avatar
  • 53
5 votes
4 answers
41k views

Cisco Router Telnet Connection Refused

I have a cisco 1941 router just configured but no matter how I go about configuring the telnet, it seems not to work. It has interfaces already set up and systems can browse through it in the office....
Laredo's user avatar
  • 569
5 votes
1 answer
500 views

"Protected" switchports on a Cisco 881W

I want to configure a Cisco 881W to deliver Corporate wired and wireless connectivity, plus Guest wireless connectivity on a second SSID, connected to the core by a site-site VPN. I was expecting to ...
user2584866's user avatar
5 votes
2 answers
2k views

Order of entries in "show ip bgp x.x.x.x"

Router# show ip bgp 10.3.3.3 255.255.255.255 BGP routing table entry for 10.3.3.3/32, version 35 Paths: (3 available, best #2, table default) Multipath: eBGP Flag: 0x860 Advertised to update-groups: ...
Eddie's user avatar
  • 15k
5 votes
3 answers
4k views

Cisco Switch (Cayalyst 2960-X): How to add a rule to the access list that filters out l2tp packet when a specific MAC address appears in it?

I am using a Cayalyst 2960-X series Cisco Switch, Whose 2 SFPs are connecting between 2 hosts (A,B). A,B are connected to the switch's 1,2 ports respectively. The host communicates using an l2tp ...
0x90's user avatar
  • 103
5 votes
1 answer
672 views

Enable traps on FIB (Forwarding Table) changes

I've been working for weeks to enable sending traps for FIB changes on our Cisco 2600 router. I finally found this command is responsible for that: snmp-server enable traps cef peer-fib-state-change ...
Tina J's user avatar
  • 235
5 votes
1 answer
531 views

Traffic marking is not working properly in QoS

Traffic marking is not working properly in QoS. I have a problem with the policy map marking bit. I would like to monitor the traffic that matches the IP precedence bit 4 in Po 50, but from the ...
Kiatbordin Jumratanet's user avatar
5 votes
1 answer
296 views

Need Zyxel Speedlink router to communicate with Cisco 886VA router

I'm trying to connect a Zyxel Speedlink router to a Cisco 886VA. The problem is that the FE ports on the Cisco 886VA are switchports and I can't assign the ports an IP address directly. Therefore, I ...
cpatte7372's user avatar
5 votes
1 answer
696 views

Time Cisco Router reload not always mentioned

Im trying to measure our cisco router availability data based on downtime happened. I assume from show version, the time mentioned in tag "System returned to ROM" is when reload started, and next line ...
hadit's user avatar
  • 53
4 votes
2 answers
600 views

Passive interface default - issue

I was trying to configure ospf router, I have a router connected to FW in G1/0/10 and mpls router connected g1/0/1, when i typed passive interface default in the ospf router i lost all connectivity ...
RR Cisco's user avatar

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