Questions tagged [cisco-ios]

For discussion about Cisco's Internetwork Operating System - Cisco IOS

Filter by
Sorted by
Tagged with
48
votes
24answers
95k views

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 ...
26
votes
4answers
108k views

How can I capture traffic on Cisco IOS switches?

For investigating a problem in client to server communication, I need to capture packets for analysis. However it's not allowed to install a packet analyzer, such as Wireshark or tcpdump, on client or ...
19
votes
3answers
8k views

What factors drive a Cisco IOS upgrade?

In order of preference/priority, what factors do you consider in driving an upgrade (or downgrade) with Cisco IOS? If no compelling factors exist, how long would you allow a particular version of IOS ...
14
votes
3answers
4k views

BGP signalled MPLS issues

I am having an issue getting a VPLS up using an ME3600x with 15.3(2) and BGP signalling. @yelfathi and @packettalk have pointed me down the correct route but not sure how to resolve it. I have 2 ...
12
votes
2answers
320 views

Do unused Cisco IOS features take up RAM/CPU resources?

For example, let's compare IP Base vs. Advanced Enterprise Services. Let's say you have advent installed, but you're only actually using the features relevant to ipbase. Other than flash memory space, ...
11
votes
1answer
1k views

Cisco IOS programming, automation, and information

I'm confused about Cisco IOS, and I have some question about that. Cisco IOS is used in routers and other devices. Is it possible to write code (like PHP) for that? If it's possible, what language ...
11
votes
1answer
10k views

How to understand “normal burst” and “maximum burst” in Cisco CAR?

As I understand, Cisco IOS CAR(Committed Access Rate) is based on leaky bucket algorithm(idea is exactly the same as token bucket algorithm) and the amount of bits I configure as average rate, is the ...
11
votes
1answer
5k views

Cisco IOS built-in SSH client default version

You issue the command ssh 192.168.97.97 from a IOS device and the destination IOS router/switch SSH server is accepting both SSH versions. Being that you did not specify a version to use on the SSH ...
11
votes
1answer
7k views

Traffic generation from Cisco IOS device to prove WAN circuit

In essence I want to know if there is any way that we can use extended ping or any other command variants to prove to the customer that that the circuit is able to achieve the minimum CIR. The CE ...
10
votes
5answers
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 | ...
10
votes
4answers
6k views

Is it possible to disable a single DHCP pool in IOS?

I am working on a Cisco L3 switch where most of SVIs are having ip helper-address configured for DHCP relay but also a couple of DHCP pools have been configured in the switch itself to serve dynamic ...
10
votes
2answers
2k views

Why does Cisco ios save and display access list entries out of order?

Consider the following access-list: access-list 25 remark city1 access-list 25 permit 10.1.120.0 0.0.0.255 access-list 25 remark city2 access-list 25 permit 10.2.120.0 0.0.0.255 access-list 25 remark ...
10
votes
2answers
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 ...
10
votes
2answers
891 views

Transaction based CLI on Ethernet Switches

I am familiar with CLI on managed Ethernet switches. However, recently I came across a term 'transaction based CLI' on switches. I am not exactly sure what is that and purpose of having it in switches....
10
votes
1answer
36k views

How can I reasonably verify my QoS configuration is working?

Context I've deployed a standard QoS config to a customer site running a Cisco 891 router with IOS 15.1(4)M4. The WAN link is a single ADSL2+ link (24/1Mbps) connected to FE8. I've previously tested ...
10
votes
1answer
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 ...
9
votes
2answers
14k views

What is Dec MOP and how to disable it?

Performing a packet capture I keep seeing strange "DEC MOP Remote Console" frames: No. Time Source Destination Protocol Info 141 83.557841 Cisco_57:62:a0 ...
9
votes
2answers
3k views

AP3602 with rcvk9w8 image throws “%CDP_PD-2-POWER_LOW: All radios disabled”

We recently bought some new AP3602Es from Cisco. I'm trying to understand why this AP will not turn on the radio when we are sending enough power to the AP. I'm using inline power from the switch, ...
9
votes
2answers
2k views

Voice VLAN information

I am aware of the ability to show the access VLAN assigned to an interface on a cisco switch. How about showing specifically the voice VLAN an interface is assigned? #show run int fa1/47 interface ...
9
votes
3answers
683 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 ...
9
votes
1answer
5k views

Suppress confirmation prompts in IOS when copying files

I am about to upgrade the IOS on several hundred Cisco VG224's in preparation for a CUCM upgrade. I am attempting to streamline/automate this process as much as possible, and currently my main ...
9
votes
2answers
5k views

Configure External Interface for DHCPv6 client on Cisco IOS

What are the necessary steps to configure IOS 12.4(25f) to support IPv6? Comcast is the ISP, and I'll be using a Server 2012 box for internal DHCPv6. I'll need to grab a DHCPv6 address from Comcast ...
9
votes
3answers
25k views

AAA/TACACS+ password on Cisco switch always fails at second password prompt

Whenever logging into a network device using AAA/TACACS+, if I fat-finger the password prompt after the username prompt, the second password prompt always fails even when the password is correct. I ...
9
votes
2answers
2k views

Are IPv6 Wildcard Matches in Cisco IOS Possible?

Facebook is very clever with their IPv6 address scheme, but it got me thinking about ACLs and Is it possible to write a Cisco IOS IPv6 ACL that matches ? In IPv4 you could match a middle octet such as ...
9
votes
1answer
2k views

Globally disable QoS on Cisco 3750 in production

I suspect some issues with faulty QoS settings on a 3750 stack running in a 24x7 environment. The 3750 mainly routes between vlans on a lan segment. Since it is a lan device (not terminating any wan ...
9
votes
1answer
16k views

What is the NO PAYLOAD ENCRYPTION version of the IOS software?

When looking at the downloads available on the Cisco site, they have a regular version of the file and a NO PAYLOAD ENCRYPTION version. What is the difference? And why would one choose one over the ...
8
votes
2answers
967 views

routing between vlans not working

I need to put a Cisco router behind an ISP router. (The ISP doesn't allow us to use their modem only.) I've called the ISP technical service and they've set up the connection with me. Their router ...
8
votes
2answers
4k views

Splitting two Internet connections between two VLANs

My current setup is as follows: Cisco 881 router (only 1 WAN interface) that has a pair of T1's coming in on the WAN interface, this currently provides internet access to two VLANs, 10 and 20. What ...
8
votes
2answers
3k views

How do I restrict a user for certain commands on Cisco IOS

I need to make a sure a certain user on an IOS router can only type specific commands. I was able to do this with privilege levels but them whenever the user would type "enable" he would be right back ...
7
votes
5answers
2k 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 ...
7
votes
4answers
53k views

Switchport mode access VLAN & switchport mode trunk on one interface

Googling around to see if this setup on one port is correct (it doesn't look right to me), I'm not really seeing a straightforward answer. There is an interface with the following configuration: ! ...
7
votes
5answers
22k views

Copy running config in one line

I want to make a script to copy the running config of a switch 4506 in one line. So far, I see two option : copy run tftp: sw#copy run tftp://10.0.0.1/cfg.cfg Address or name of remote host [10....
7
votes
3answers
6k views

Edit Cisco IOS ACL without hanging the router

I have a Cisco Router 1941 Series and I want to make some changes to the access-list on the router. I got to know I will have to delete one of the list and then re-add everything again with my ...
7
votes
2answers
15k views

Securing Cisco device from brute force attacks

I'm trying to block users from configuring a Cisco IOS device if they have entered incorrect passwords a number of times. This is the command I'm using: Router(config)# login block-for 120 attempts 3 ...
7
votes
4answers
777 views

Cisco IOS cli prompts - any way to know which interface you are configuring?

I'm used to the Juniper and Extreme worlds more than Cisco. I'm able to get by OK, but some basic cli issues arise that have finally frustrated me enough. Inside a Cisco ASA 5505/5510 running 8.3+ ...
7
votes
1answer
507 views

Cisco IOS Tcl - Overhead

I've not been able to find much in regards to TCL other than the Cisco PDF "Cisco IOS Scripting with TCL Configuration Guide" and I just have a few queries. I'm looking into potentially utilising ...
7
votes
1answer
10k views

Using a Cisco router as an L2TP client?

I have a customer that for various reasons has a Cisco router sitting behind a NATed ADSL connection. They want to create a VPN to one of our points of presence and the only options we offer are site ...
7
votes
1answer
6k views

Configuring a password policy on Cisco IOS or NX-OS

I was wondering if it's possible at all to configure a password policy which enforces password complexity for locally defined accounts. I know it's possible for TACACS+ and RADIUS, but I need to know ...
7
votes
1answer
8k views

Mitigating a IPv6 malformed packet multicast flood

So we just had our first IPv6 multicast flood in the network this morning. We managed to stop the offending computer by blocking the mac address with: mac-address-table static x.x.x vlan x drop ...
7
votes
2answers
1k views

Multiple WANs/Out-of-band (Cisco 1900)

I've got a Cisco 1900 router which connects to the Internet using a primary and a secondary WAN connection. When the primary connection is up, all traffic use this link. When the primary connection ...
7
votes
2answers
6k views

Cisco 3064 switch upgrade from 6.0.x to 7.0.x issue

I am trying to upgrade from 6.0.2.U6.5c to nxos.7.0.3.I4.7, before upgrade i want to make sure it pass all checks but i got this error. This switch isn't in production yet but want to make sure it ...
7
votes
4answers
9k views

SCP lost connection

Occasionally I have an issue when I try to SCP a file to one of our Cisco devices. When the connection starts, it immediately drops and says "lost connection". I've had this happen when there wasn't ...
7
votes
1answer
3k views

What is benefit of using CBWFQ with fair-queue statement

I mostly seeing configuration of QoS queues based on CBWFQ, witch is tripped off by shaping map. Something like below example. policy-map test class test bandwidth remaining percent 20 random-...
7
votes
1answer
817 views

How to break apart an IPv6 /56 6rd delegated prefix from ISP into multiple /64 VLANs for use with SLAAC EUI-64? [Cisco]

I have CenturyLink Internet service, and they have a 6RD IPv6 deployment where they hand out an IPv6 delegated prefix /56 block to me and allow me to use it as I wish. My Cisco ISR router receives the ...
6
votes
2answers
27k views

What are the different modes in Cisco routers, and why these modes?

I want to know on what basis Cisco designed the different modes in their routers. For example: config mode execution mode Can any one give the perfect reasons behind the different modes? What ...
6
votes
2answers
2k views

Devices that utilizes CISCO IOS Operating system

I am a bit confused about the CISCO IOS operating system. My final year research project is based on solving some security vulnerabilities that i dug up that exists in the CISCO IOS, thus i need to ...
6
votes
4answers
49k views

How can I view bandwidth use by ip/host on a Cisco router?

My company has a 100mbps Internet connection and we have recently experienced extreme slowness when using the Internet (our provider's speedtest page indicated .25 Mbps download speed). When we ...
6
votes
2answers
1k 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 ...
6
votes
2answers
1k views

How to run a CAM Table Overflow attack in GNS3 using Cisco 3725 routers?

I am currently working on MiTM attacks and defenses in a virtual environment using GNS3 and an IOS c3725 (c3725-adventerprisek9-mz.124-15.T14) image to emulate some topology. The current experiment ...
6
votes
1answer
20k views

What is the difference between “permit tcp any any eq telnet” and “permit tcp any eq telnet any”?

I'm a CCNA student and during a LAB I found that for some rules on an incoming extended ACL using a rule like permit tcp any any eq (protocol) would work fine while on other rules I needed to use the ...

1
2 3 4 5
11