18 votes
Accepted

Cisco IOS programming, automation, and information

Almost everyNote 1 Cisco IOS system running at least IOS 12.2 has built-in tcl shell programmability. You can store tcl scripts in flash and run them. Cisco IOS also has a light native programming ...
Mike Pennington's user avatar
13 votes

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? For the simple reason that the only the major and minor versions are necessary for a complete ...
YLearn's user avatar
  • 27.3k
12 votes
Accepted

How to Disable telnet on Cisco switch totaly?

If you actually configured line vty 04 Then you have something like: line vty 0 3 transport input telnet ssh line vty 4 transport input ssh This is because you configured only the fifth VTY ...
JFL's user avatar
  • 19.6k
11 votes
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Meaning of the ip default-gateway L2 switch

tl;dr The switch management cannot send anything to a different layer-3 network without a default gateway. Telnet is a bidirectional protocol, and the switch, without the default gateway, would be ...
Ron Maupin's user avatar
  • 99.4k
11 votes

routing between vlans not working

You don't have NAT enabled (you don't have ip nat outside on Vl 20). Without NAT, the ISP doesn't know how to route back to your 192.9.200.0 network. If you NAT to the VLan 20 address, the ISP ...
Ron Trunk's user avatar
  • 67.3k
11 votes
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Why does the CISCO's command 'enable secret <password>' produce different hash from MD5?

Cisco devices add a salt to the passwords before hashing so they can't be cracked with dictionary attacks (such as rainbow tables). The salt is partially made up of the device ID, if I recall. MD5 is ...
Jesse P.'s user avatar
  • 4,690
10 votes

Why does the CISCO's command 'enable secret <password>' produce different hash from MD5?

$1$ marks the MD5-crypt password hash also commonly used in past years for user passwords in Linux systems. In that function, it's now been pretty much superseded by the similar SHA256-crypt and ...
ilkkachu's user avatar
  • 407
9 votes
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Cisco IOS versions vs Cisco ASA versions?

Cisco has a whole bunch of different operating systems for a variety of products: IOS runs on most Cisco routers and switches. IOS XE is a more modern, modular version of IOS. IOS XR runs on high-end ...
RobinG's user avatar
  • 1,969
8 votes

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

The two forms are equivalent. "domain-name" is the older form, and newer versions seem to prefer "domain name". Maybe at some point Cisco realized that removing the hyphen allowed them to extend the "...
mere3ortal's user avatar
  • 2,416
8 votes
Accepted

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

They are the same. Cisco IOS also supports the command ip domain name starting from its 12.2 Software release. You can check it here: IOS: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr/...
Hung Tran's user avatar
  • 3,754
8 votes
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Why is option 82 required for DHCP when you use `ip verify source port-security`?

How is this different than using port security or ip source guard alone and why is option 82 required for this to work? When you add the MAC address source filtering to IP source guard using the ip ...
YLearn's user avatar
  • 27.3k
8 votes
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When and where to use Spanning-Tree (Portfast)

Spanning tree only runs between switches, never to standard end hosts. Bear in mind that, under normal circumstances, a port supporting spanning tree will (when it first comes up) run through a ...
rnxrx's user avatar
  • 6,114
8 votes
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Configuring OSPF on two directly connected routers which are in different areas

In order to connect two areas, one router has to serve as an area border router (ABR). That router has interfaces in both areas. In other words, the boundary between two areas is a router, not the ...
Ron Trunk's user avatar
  • 67.3k
7 votes

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

First and foremost, I must indicate that I am mostly active on the IT Security StackExchange website. Since this current website may reach a different public I find it wiser to tell that, while I ...
WhiteWinterWolf's user avatar
7 votes
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Why is Cisco enforcing X:X:X:X::X for link-local addresses when the standard says FE80:/10?

The document to which you link claims a specific IOS version. It may be incorrect; that would not be unusual in Cisco documentation. In reality, having tested this on several IOS 15.X versions, you ...
Ron Maupin's user avatar
  • 99.4k
7 votes
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Best practice for advertising routes in BGP

You are conflating two different issues: Route-maps can act as a policy filter, selecting which prefixes are advertised to neighbors and which are accepted from neighbors. Advertise-maps allow you ...
Ron Trunk's user avatar
  • 67.3k
7 votes
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Config logging on which cisco IOS?

Almost every Cisco IOS router 12.x and 15.x supports this command. You can use it in this way to send configuration command logging to syslog server: conf terminal archive log config logging ...
Andrey Prokhorov's user avatar
7 votes
Accepted

routing between vlans not working

The problem is that you have not defined the ACL that tells the router which addresses to translate. You have: ip nat inside source list nat-list interface GigabitEthernet2 overload but you do not ...
Ron Maupin's user avatar
  • 99.4k
7 votes
Accepted

Fix our Cisco switch overwhelmed by console logging

I have a setup with dual redundant Cisco catalyst 4506-E using the WS-X45-SUP8L-E supervisor engine and two 48-port switches below it. My task is to access and modify the switch configuration. ...
Mike Pennington's user avatar
7 votes

Cisco APIC command equivalent to Cisco IOS `show terminal | include Length`

You have encounter a software bug: CSCva24843 Below is a copy/paste from Cisco Bug Search: ACI | Shorthand for "terminal length 0" does not work CSCva24843 Symptom: User enters "term len 0" to ...
Cow's user avatar
  • 1,732
6 votes
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Cisco IOS CLI -- Difference between global configuration and console line configuration mode (using line console 0 command)?

Global configuration mode is for configuring global parameters. This is the default mode when you enter configuration mode. Some commands will cause you to enter a more specific configuration mode. ...
YLearn's user avatar
  • 27.3k
6 votes
Accepted

Cisco: err-disabled due to loop - but there are NO redundant physical paths/ wires/ connections

I think this might be related to a bug. This issue is documented in Cisco bug ID CSCea46385. To resolve the issue, you need to add the no keepalive command to the interface. Hope this helps you on ...
SleepyMan's user avatar
  • 2,016
6 votes
Accepted

Can I connect to Cisco router's AUX port from a switch Ethernet port?

The AUX port is basically a serial port and is not an Ethernet port at all, so no you can't connect it to an ethernet switch port. But you can connect a RTC modem to it and access the console ...
JFL's user avatar
  • 19.6k
6 votes

Factory Reset Cisco 3560: Stuck in loop

Sounds like a nice job of a botched content ot the boot variable - possibly the config file variable. The switch: prompt you see there is called the ROMMON prompt. ROMMON is a bit like the BIOS of a ...
Marc 'netztier' Luethi's user avatar
6 votes
Accepted

Virtual Appliance - Cisco Router

The IOS XRv 9000 is probably a bit of an oddball - it's IOS-XR based. I never got round to get my hands on it or any other device running IOS-XR. That's carrier and service provider grade stuff, and ...
Marc 'netztier' Luethi's user avatar
6 votes
Accepted

Client timeout for Cisco IOS Static DHCP Pool

It looks like your configuration for the DHCP reservation is incorrect. It seems you only have the hardware address (used for BOOTP) missing the network type, but not the client identifier (used for ...
Ron Maupin's user avatar
  • 99.4k
6 votes

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

To put it in other words... The running-config has a version listed because that's the version of IOS that was used to create/write that config most recently. Every statement in that config should ...
Criggie's user avatar
  • 717
6 votes

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

I would have said the numbers represent different things: show version says "I am running this version", and of necessity has much detail version output in show conf says "This configuration will run ...
jonathanjo's user avatar
  • 16.2k

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