Questions tagged [cisco-ios]

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

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48
votes
24answers
92k 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 ...
23
votes
4answers
106k 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 ...
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 ...
2
votes
1answer
460 views

Cisco Prefix List Won't Appear in Route Table

I have the following prefix-list configured on our router: ip prefix-list adsvr seq 5 permit 172.30.5.241/32 ip prefix-list adsvr seq 10 permit 134.239.130.143/32 ip prefix-list adsvr seq 15 permit ...
19
votes
3answers
7k 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 ...
7
votes
5answers
21k 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....
10
votes
2answers
835 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....
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
2answers
14k 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 ...
6
votes
1answer
5k views

AAA Authorization Timeout

Log into a Cisco IOS device with TACACS Authorization enabled Do a command that causes the device to lose access to the TACACS server Enter a command that requires TACACS Authorization By default, ...
6
votes
1answer
4k views

Cisco OSPF type 5 /32 routes in database, but not in routing table

Our network runs OSPF for IPv4 on Cisco hardware. The following image shows the relevant topology: Topology Problem Statement We have a Cisco ASA firewall, which also is the VPN gateway for ...
5
votes
4answers
48k 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 ...
4
votes
1answer
2k views

Cisco ASA RRI and OSPF redistribution

This is a follow-up question based on this original question. The following topology is present: The Cisco ASA is our Internet firewall, as well as VPN gateway, terminating VPN connections. The ASA ...
4
votes
2answers
22k views

SNMP: Configuring/Enabling SNMPv3 on Cisco IOS and SNMP Agent

I have been configuring and using SNMP v2c on Cisco routers. Due to the obvious advantages in SNMP v3, I am planning on enabling SNMP v3 on SNMP v3 supported devices. Could someone let me know: The ...
4
votes
3answers
18k views

Meaning of the ip default-gateway L2 switch

What is meaning of the ip default-gateway command on a Cisco L2 switch? I read something about it on the Internet, but there was written that it allows you to Telnet to the switch. I am little bit ...
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 ...
7
votes
4answers
739 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
5k 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 ...
6
votes
1answer
3k views

console connection via Cisco router's AUX port

my question is simple: if I am logged into a Cisco router via console or ethernet in priviledged mode, is there a command to initiate a connection through the local AUX port to a nearby console port ...
5
votes
1answer
180 views

What happens at the hardware level of a router when a packet is received and eventually triggers a process like ARP?

Please let me know where the gaps in my understanding are. There are many gaps, so please do not hesitate to fill them in or correct them. To my knowledge, what happens on the hardware level when ...
5
votes
2answers
1k views

Cisco IOS - Is it possible to change severity level of a single syslog message?

On an ASA I can change the severity of a single syslog message by doing this: logging message 713120 level notifications Is there a way to do this on a Cisco Router running 15.1 code? I am only ...
5
votes
1answer
13k views

How To Limit a VLAN to a Specific Bandwidth Quota

I have a Cisco Router 1900 series and I would like to limit the bandwidth used by a subnet/subinterface. This subnet/subinterface (192.168.10.*) uses most of the bandwidth making it useless for other ...
5
votes
1answer
934 views

Why is option 82 required for DHCP when you use `ip verify source port-security`?

Learning about security features on Cisco switches and came across the requirement to use option 82 with DHCP when you enable ip verify source port-security on an interface. How is this different ...
5
votes
1answer
2k views

Cisco process memory usage

I am trying to monitor a Cisco process memory usage. This is what I get with the command line: show system internal processes memory | inc PID|ipfib PID TTY STAT TIME MAJFLT TRS RSS ...
4
votes
2answers
2k views

Cisco - MtR alternatives

I trying to establish if there is a function within IOS somewhere that can provide the same results of MTR , i know it can be run from Juniper devices / *Nix & Windows devices. Goal is to ...
3
votes
1answer
1k views

Junos feature to accept multiple BGP paths from multiple peer AS

Cisco IOS provides this hidden BGP command: router bgp <ASN> bgp bestpath as-path multipath-relax It allows the router to install multiple BGP prefixes with distinct as-path'es (but ...
3
votes
1answer
5k views

How to erase running-configuration in Cisco IOS-XE?

I am using ASR 9k series Routers, which runs IOS-XE advancedmetroipaccess License I tried erasing NVRAM: and then tried to run copy start run But it gives me error : hostname#erase /all nvram: ...
3
votes
2answers
5k views

Run out of ideas to troubleshout Ping issue Cisco IOS 3560 Switch

Summary Yesterday, four of the eight systems (connected to same VLAN, identical ethernet adapter settings) were able to ping tweakers.net. Today, another system is not able to ping the internet ...
3
votes
2answers
90 views

Client timeout for Cisco IOS Static DHCP Pool

I'm not a network admin, but I have an old Cisco Catalyst 3560 for my network. I've successfully set up a DHCP Pool: ip dhcp pool 192.168.0.0 network 192.168.0.0 255.255.255.0 default-router 192....
3
votes
1answer
681 views

Routing Between VLANs on Cisco 1921

I have setup a new VLAN for VoIP phones that are being installed. I would like to segment their traffic to Subnet 10.20.77.0/24. I added an IP address to the DHCP server of 10.20.77.11 to help serve ...