Cisco Commands - Revision history

209.87.206.13: /* Configuration Files */

2026-02-25T02:10:08Z

Configuration Files

← Older revision		Revision as of 02:10, 25 February 2026
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	== Configuration Files ==		== Configuration Files ==

			=== Erase Configurations ===
			erase startup-config
			delete flash:vlan.dat

	=== Show Configurations ===		=== Show Configurations ===

209.87.206.13: /* Spanning Tree */

2026-02-25T01:52:15Z

Spanning Tree

← Older revision		Revision as of 01:52, 25 February 2026
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	=== Set the Root Bridge ===		=== Set the Root Bridge ===
	~~Define a~~ root bridge ~~to control~~ the topology ~~and ensure consistent path selection~~.		The root bridge is the central switch in the spanning tree topology. It is chosen based on the lowest bridge priority. A lower priority value increases the likelihood of a switch becoming the root bridge.

	Set priority to influence root bridge selection:		Set priority to influence root bridge selection:
			* The default priority value is 32768 for all switches.
			* Priority is set in increments of 4096, and this value is added to the VLAN ID (e.g., for VLAN 1, the default bridge priority would be 32768).

			To influence the root bridge selection, change the priority value:
	interface GigabitEthernet0/1		interface GigabitEthernet0/1
	spanning-tree vlan 1 priority 4096		spanning-tree vlan 1 priority 4096
			(Sets a lower priority value, increasing the likelihood of this switch becoming the root bridge for VLAN 1)

	Set the root bridge for a specific VLAN:		Set the root bridge for a specific VLAN:
			* To make the current switch the root bridge:
	spanning-tree vlan 1 root primary		spanning-tree vlan 1 root primary
	(This sets the ~~local~~ switch as the root bridge)		(This automatically sets the priority lower than the default value, typically to 24576, to ensure this switch becomes the root bridge)

	~~Alternatively, set it to secondary~~:		* To make the current switch the backup root bridge:
	spanning-tree vlan 1 root secondary		spanning-tree vlan 1 root secondary
	(This sets the ~~local~~ switch to be the ~~backup~~ root bridge)		(This sets the priority higher than the primary root, typically to 28672, making it the backup root bridge)

			Alternatively, manually set the root bridge priority:
			interface GigabitEthernet0/1
			spanning-tree vlan 1 priority 24576
			(Sets this switch with a higher priority, making it more likely to become the root bridge)

	=== Verify Root Bridge ===		=== Verify Root Bridge ===

	show spanning-tree vlan 1		show spanning-tree vlan 1
			(Shows the current root bridge and its priority, along with other STP details)

	=== Notes ===		=== Notes ===
	* Do '''not''' enable PortFast on ports connected to other switches		* Do '''not''' enable PortFast on ports connected to other switches (this can cause network loops).
	* ~~Recommended for~~ access/edge ports		* PortFast should only be used on access/edge ports that connect to end devices like PCs, printers, or phones.
	* Incorrect use can cause Layer 2 loops		* Incorrect use of PortFast can cause Layer 2 loops.
	* ~~Root Bridge selection can impact the STP topology~~ and ~~performance~~		* The default priority value is 32768, and it is adjusted in increments of 4096.
	* Lower priority values increase the ~~chance~~ of becoming the root bridge		* Lower priority values increase the likelihood of becoming the root bridge.
			* The priority value combined with the MAC address (if priorities are equal) is used to determine the root bridge.

	== DHCP Snooping ==		== DHCP Snooping ==

209.87.206.13: /* Spanning Tree */

2026-02-25T01:50:58Z

Spanning Tree

@@ Line 422: / Line 422: @@
   spanning-tree portfast default
   spanning-tree bpduguard default
 === Notes ===
@@ Line 427: / Line 446: @@
 * Recommended for access/edge ports
 * Incorrect use can cause Layer 2 loops
 == DHCP Snooping ==

50.220.241.211: /* SSH Configuration */

2026-02-24T19:55:27Z

SSH Configuration

← Older revision		Revision as of 19:55, 24 February 2026
Line 150:		Line 150:
	ip ssh version 2		ip ssh version 2
	</pre>		</pre>

			=== Generate RSA Keys (1-liner) ===
			crypto key generate rsa general-keys modulus 1024

	=== Remove RSA Keys ===		=== Remove RSA Keys ===

50.220.241.211: /* Configure a Static Route */

2026-02-23T23:07:18Z

Configure a Static Route

← Older revision		Revision as of 23:07, 23 February 2026
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	=== Configure a Static Route ===		=== Configure a Static Route ===
	Manually define a path to a remote network. Here's an example using default administrative distance ~~values listed in the section below~~.		Manually define a path to a remote network. Here's an example using the default administrative distance value.

	ip route 192.168.2.0 255.255.255.0 192.168.1.1		ip route 192.168.2.0 255.255.255.0 192.168.1.1

	Manually define a path to a remote network~~. Here's an example manually defining~~ the administrative distance		Manually define a path to a remote network and specify the administrative distance.

	ip route 192.168.2.0 255.255.255.0 192.168.1.1 10		ip route 192.168.2.0 255.255.255.0 192.168.1.1 10

	Format:		Format:
	ip route <destination-network> <subnet-mask> <next-hop-ip> <administrative distance (optional)>
			ip route <destination-network> <subnet-mask> <next-hop-ip> <administrative-distance (optional)>


			=== Configure a Fully Specified Static Route ===
			A fully specified static route includes both the next-hop IP address and the exit interface. This is commonly used on multi-access networks.

			Example:

			ip route 192.168.2.0 255.255.255.0 GigabitEthernet0/0 192.168.1.1

			You can also specify the administrative distance:

			ip route 192.168.2.0 255.255.255.0 GigabitEthernet0/0 192.168.1.1 10

			Format:

			ip route <destination-network> <subnet-mask> <exit-interface> <next-hop-ip> <administrative-distance (optional)>

	=== Configure a Default Route / Default Gateway ===		=== Configure a Default Route / Default Gateway ===

50.220.241.211: /* Administrative Distance */

2026-02-23T22:43:32Z

Administrative Distance

← Older revision		Revision as of 22:43, 23 February 2026
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	RIP – 120		RIP – 120

			Chart pulled from https://en.wikipedia.org/wiki/Administrative_distance#Default_administrative_distances
	{\| class="wikitable" style="text-align:center"		{\| class="wikitable" style="text-align:center"
	! Routing protocol !! Administrative distance		! Routing protocol !! Administrative distance

50.220.241.211: /* Administrative Distance */

2026-02-23T22:42:30Z

Administrative Distance

@@ Line 631: / Line 631: @@
 {| class="wikitable" style="text-align:center"
-! Routing protocol !!  Administrative distance
+! Routing protocol !! Administrative distance
 |-
-| Directly connected interface || 0{{efn|Only the interface itself has an administrative distance of 0, since a route cannot have a distance of less than 1.}}<ref name="Cisco AD">{{citation |title=Default AD |url=http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/15986-admin-distance.html#topic2 |author1=Cisco}}</ref>
+| Directly connected interface || 0 (Only the interface itself has an administrative distance of 0, since a route cannot have a distance of less than 1.)
 |-
 | Static route || 1
 |-
-| [[Next Hop Resolution Protocol]] (NHRP) || 250<ref name="Cisco NHRP">{{citation |title=NHRP |url=https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_nhrp/command/reference/irn_book/nhrp-commands--a-through-z.html#wp8534493760 |author1=Cisco}}</ref>
+| Dynamic Mobile Network Routing (DMNR) || 3
 |-
-| Default static route learned via DHCP || 254{{citation needed|date=October 2018}}
+| Unknown and unused || 255 (An administrative distance of 255 causes the router to remove the route from the routing table and not use it.)
 |}

50.220.241.211: /* Administrative Distance */

2026-02-23T22:40:00Z

Administrative Distance

@@ Line 629: / Line 629: @@
   OSPF – 110
   RIP – 120
 == Dynamic Routing ==

50.220.241.211: /* Assign IPv4 Default Route / Default Gateway (Router) */

2026-02-23T22:36:05Z

Assign IPv4 Default Route / Default Gateway (Router)

← Older revision		Revision as of 22:36, 23 February 2026
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	=== Assign IPv4 Default Gateway (Switch) ===		=== Assign IPv4 Default Gateway (Switch) ===
	ip default-gateway 192.168.0.254		ip default-gateway 192.168.0.254

	~~=== Assign IPv4 Default Route / Default Gateway (Router) ===~~
	~~ip route 0.0.0.0 0.0.0.0 192.168.1.1~~

	~~----~~

	== Interface IPv6 Configuration ==		== Interface IPv6 Configuration ==

50.220.241.211: /* Set Default Gateway */

2026-02-23T22:35:48Z

Set Default Gateway

← Older revision		Revision as of 22:35, 23 February 2026
Line 161:		Line 161:
	</pre>		</pre>

	=== Set Default Gateway ===		=== Set Default Gateway (switch) ===
	<pre>		<pre>
	ip default-gateway 192.168.10.1		ip default-gateway 192.168.10.1