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14 votes
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What does no shutdown command do? Cisco

In the simplest sense, shutdown turns the interface off. no shutdown turns the interface on (enables it). You can configure an interface in either case. Using the shutdown command is one of the ...
Ron Trunk's user avatar
  • 67.6k
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
  • 27.4k
12 votes
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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
  • 19.7k
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 In that function, it's now been pretty much superseded by the similar SHA256-crypt and ...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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Locked myself out of my Cisco switch

If you didn't save the configuration, you could just restart the switch, but you will need physical access to the switch. You may be able to get someone at the site to restart the switch for you. ...
Ron Maupin's user avatar
  • 99.8k
9 votes
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Duplex Mismatch Detection

Packet Tracer is a simulator aimed at CCNA level courses. It doesn't accurately simulate real devices but only a subset of their functions. (and still those simulations aren't perfect). I would not ...
JFL's user avatar
  • 19.7k
8 votes
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How IP helper address works?

Using the ip helper-address command sets up a DHCP relay. DHCP only works on the LAN to which it is connected because it uses broadcast, which cannot cross a router. To remedy that situation, DHCP ...
Ron Maupin's user avatar
  • 99.8k
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
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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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set cli complete-on-space Cisco equivalent

The Cisco command completion uses the <TAB> key (one of the Juniper options). Cisco commands also do not even need to be complete to work; they only need to be complete enough to be unambiguous....
Ron Maupin's user avatar
  • 99.8k
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
  • 99.8k
7 votes
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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
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spanning tree RootGuard question on vPC switches

Based on the comments I think you are confused about guard root. You configure guard root on the downstream interfaces of all the switches, except the root switch. Basically, you are trying to protect ...
Ron Maupin's user avatar
  • 99.8k
7 votes
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Cisco show log number of messages

If you’re using ‘show log’ to display messages in the logging buffer, then you’re using IOS or IOS-XE. In both of those Cisco operating systems there is a default syslog buffer size (configured in ...
Mike Pennington's user avatar
6 votes

How IP helper address works?

To add to Ron's great answer: The key piece of this is that the Router sending the DHCP request on behalf of the client will unicast the request with a source address from the address space the ...
HostBits's user avatar
  • 636
6 votes
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What commands do I run to change IP NAT settings for a Cisco 2800 series router

Simply use the "no" form of the command to remove the first statement, then add the second one. Like this: config t no ip nat inside source static tcp 172.*.*.1 80 117.218.*.* 80 extendable ip nat ...
Ron Trunk's user avatar
  • 67.6k
6 votes
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EHWIC-1GE-SFP for Cisco 1941

You can change to the SFP interface. Under the interface configuration, configure: media-type sfp To change back to the copper interface: media-type rj45
Ron Maupin's user avatar
  • 99.8k
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
  • 737
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
  • 16.3k
6 votes

How to connect QSFP+ transceiver with MPO connector and SFP+ transceiver with LC connector?

You need a breakout cable - MPO to 8x LC. The reach of the cable depends on the PHY that is used, e.g. 400 m for 10GBASE-SR over OM4, or 10 km for 10GBASE-LR over OS2. Make sure that the transceivers ...
Zac67's user avatar
  • 84.9k
6 votes

Passive interface default - issue

A passive interface in OSPF does not send hello packets, so it will never form a neighbor relationship nor exchange routes with another OSPF router. By setting the passive interface default command, ...
Ron Trunk's user avatar
  • 67.6k
5 votes

How to know the interface utilization on a Cisco switch?

What you are looking at is the bit rate over the last five minutes. You can change the time period, but not below 30 seconds with the load-interval command. I'm not sure what you mean by "utilization....
Ron Maupin's user avatar
  • 99.8k
5 votes

Cisco - Changing LACP rate from slow to fast

Based on my tests changing the LACP rate bounces the Port-Channel: *Jan 6 04:08:08.204: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/15, changed state to down *Jan 6 04:08:08....
Mikis's user avatar
  • 51
5 votes
Accepted

How does a Cisco ACL handle fragments

You are not denying fragments. Cisco has an Access Control Lists and IP Fragments document that specifically deals with this problem. ACLs and Fragmented Packets ACLs have a fragments keyword ...
Ron Maupin's user avatar
  • 99.8k
5 votes
Accepted

Why do I get different serial number from "show version" than from "show inventory"

Show inventory is for local information only. You are finding the serial number of the 1000BaseLX SFP optic in Gi1/0/9 with this output. The show inventory and show version on the 2960 should match. ...
cpt_fink's user avatar
  • 1,470
5 votes
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List interface names and MAC addresses on Cisco device?

You can roughly accomplish this by regex'ing the show interfaces command: show interfaces | i (.* line protocol is )|(.* address is) This will produce fairly concise output with the interface on one ...
boomi's user avatar
  • 993
5 votes

Telnet or SSH into a Cisco router

You'll need to have a hostname and a domain and generate the keys for ssh to work. My notebook says: hostname gw99 ip domain name example.com crypto key generate rsa modulus 2048 ip access-list ...
jonathanjo's user avatar
  • 16.3k

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