Names for special characters on keyboard

I am not sure if school teaches the names for special characters/signs on keyboard in English speaking countries, but we did not have these taught in School or at least shown in text book in China.

So if you have no knowledge or limited knowledge of the names for keyboard signs, here you have the list to help you:

‘~’ -> ’tilde dash’

‘`’ -> ‘backquote’

‘!’ -> ‘exclamation mark’

‘@’ -> ‘at sign’

‘#’ -> ‘number sign’ or ‘hash’ or ‘pump sign’

‘$’ -> ‘dollar sign’

‘%’ -> ‘percentage sign’

‘^’ -> ‘caret sign’

‘&’ -> ‘ampersand’

‘*’ -> ‘asterisk’ or ‘star sign’

‘(‘ -> ‘parenleft’ or ‘opening parentheses’

‘)’ -> ‘parenright’ or ‘closing parenteses’

‘-‘ -> ‘minus’

‘_’ -> ‘underscore’

‘+’ -> ‘plus’

‘=’ -> ‘equal’

‘{‘ -> ‘braceleft’

‘[‘ -> ‘bracketleft’

‘}’ -> ‘braceright’

‘]’ -> ‘bracketright’

‘|’ -> ‘bar’

‘\’ -> ‘back slash’

‘:’ -> ‘colon’

‘;’ -> ‘semicolon’

‘”‘ -> ‘double quote’

”’ -> ‘single quote’

‘<‘ -> ‘less than sign’

‘,’ -> ‘comma’

‘>’ -> ‘greater than sign’

‘.’ -> ‘period’

‘?’ -> ‘question mark’

‘/’ -> ‘forward slash’

‘ ‘ -> ‘space’

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Recovery Cisco router/switch login password

There might be tons of same topic on Inter-Web, especially on Cisco website, but I still decide to post it, at least I can archive in case I lost computer or notebook…

Cisco Router/Switch Password Recovery:

1. Apply break during the device booting sequence: Mostly the “Ctrl + Break” will work. I use putty 99% of time and putty needs to be configure/accessed via clicking the left mouse button on the icon in the top left corner of PuTTY’s terminal window to see the special command “break”.

2. Set configure register: rommon 1> confreg 0x2142

3. Reset the device: rommon 2> reset

4. Type no after each setup question, or press Ctrl-C in order to skip the initial setup procedure.

5. Type configure memory OR copy start run

6. Change password(s) when device boots up completely

7. Restore the config register: hostname(config)#config-register 0x2102 <– REMEMBER TO DO IT

8. Type write memory or copy running-config startup-config in order to commit the changes.

9. Reload device.

NOTE, all interfaces are shutdown when doing password recovery. So manual “no shut” is needed for each interface.

For recovering password for Cisco ASA, check here.

See Also: Cisco Reference

Processor Load Troubleshooting Tips

Apply to IOS Cisco gears ONLY:

Router#show processes cpu | exclude 0.00%__0.00%__0.00%

Router#show processes cpu | include CPU|IP Input

Router#show processes cpu history

Router#show processes | include ARP Input <- ARP messages orginated from router itself. There will be a lot of the ARP message sent out if router has to keep asking for Mac address of the next hop.

Router#show processes | include Net Background <- process used to create packet buffer when hardware buffer is full. If also the interfaces also loaded, it could also have this process loaded.

Router#show processes | include IP Background <- handle the configuration change for interface. Maybe a bad interface flapping up and down could cause issue.

Router#show processes | include TCP Timer <- handle the TCP session terminated on router itself. A lot of ssh/telnet/https sessions to router for management could increase the processor load.

•Check the default route setting on router. It is better to set default route to an address instead of the broadcast interface, like the fast ethernet interface, to avoid keep generating ARP Messages.
•Check the interface throttles, overruns, ignores in “show interface” command, which could increase the load.
•Run “Router#show tcp statitics” to see the statistics of connections.
•Run “Router#show tcp brief” to see sessions to router/switch as management connection.
•Hacker could generate thousands of connections to DoS of router. So put some access-list on VTY to protect remote management.

If you find the above looks familiar, study the CCNP yourself, you might write some fancier ones 🙂

Memory Load issue on Cisco gear

Cisco gear possible memory Load issue:
•Pay attention to log message, like ‘%SYS-2-MALLOCFAIL: …’ on Cisco device, run to the device to reboot it. The memory is leaking bad!! I found this: ‘%SYS-3-INVMEMINT: Invalid memory action (free) at interrupt level’ on Cisco 1920 router with IOS 15.1(4)M3 and Cisco openned a bug (#CSCtx59639). But not sure when there can be a fix…
•If “show” commands show nothing but blank screen, there is something wrong with memory on device.
•From serial console: “Unable to create Exec – No Memory OR Too many Processes”, that means something is wrong related memory.
•If wrong IOS image loaded, could be because of not enough memory.
•If bug in IOS image, there could be memory leak.
•Worn or Virus focus on IOS
•BGP could also load memory

If you find the above looks familiar, study the CCNP yourself, you might write some fancier ones 🙂

High Interface Utilization?!

Is it really possible that Interface utilization could cause issue on Cisco gear? Yes!!
•If there are a lot of collision OR late collision in “show interface” command, there might be a duplex mismatch. Especially when you connect a router external interface to a half-duplex modem…
•If there are High CPU utilization, packet drop, unreachable destinations, there could be something loaded on interface.
•Check the switching mode on device:
◦Process Switch: Check header of every single packets received for requesting next hop ARP and routing.
◦Fast Switch: Check header for very first packet and cache the record for rest of the packets. There is still potential issue with handling the first packet.
◦CEF(Cisco Express Forwarding): When router boots up, it pre-caches all the ARP results according to the routing table. So when packets arrive, it just forward according to caches.
•Check the routing table for the routes
•Check CEF / ARP Cache

If you find the above looks familiar, study the CCNP yourself, you might write some fancier ones 🙂

Tips for L2/L3 Switches troubleshooting

Not many things can go wrong on Switch level, but issues are also difficult to troubleshoot there.

L3 Switching and Redundancy: VLANs and Routing will be the main section to check for issues on L3 switches(maybe L2 also)

Switch#show brief

Switch#show

Switch#debug terse <- Only show the debug message except HELLO message

Spanning Tree:

Switch#show spanning-tree

Switch#show spanning-tree detail

Switch#show process cpu

If the troubleshooting goes to dead end, try to shutdown interfaces based on “Switch#show cdp neighbors” output to find the loop.

If you find the above looks familiar, study the CCNP yourself, you might write some fancier ones 🙂

Big Routing could go wrong…EGRP

L3 Routing and EIGRP:
Router#show ip route

Router#show ip arp / frame map / etc …

Router#show ip eigrp neighbors

Router#show ip eigrp topology

Router#show ip eigrp iinterfaces

Router#debug ip eigrp neighbor / packets

Double check the network statement under router eigrp process to make sure proper network is advertised

If you find the above looks familiar, study the CCNP yourself, you might write some fancier ones 🙂

Big Routing could go wrong…OSPF

OSPF and Route redistribution:

Router#show ip ospf neighbors

Router#show ip ospf interface <- pay attention to the dead/hello timers

Router#show ip ospf database

Router#debug ip ospf adj / packets

Router#debug ip routing

Router#clear ip ospf process

•When redistribute routes between different routing protocol, pay attention to the seed metric. If do not set the seed metric, EIGRP/RIP will by default set the metric of routes from other routing protocol to be infinite; OSPF will by default set the metric of routes from other routing protocol to 20; BGP will keep the same metric value when routes enter BGP.
•When do full bi-directional route redistribution between 2 routing protocols, there could be route loop. So apply proper filters to limit the route.

If you find the above looks familiar, study the CCNP yourself, you might write some fancier ones 🙂

Big Routing could go wrong…BGP

BGP:

Router#show ip bgp summary <- brief neighbor list and memory usage

Router#show ip bgp

Router#show ip bgp neighbors

Router#debug ip bgp

Router#debug ip bgp updates #- use it with caution!!

If you find the above looks familiar, study the CCNP yourself, you might write some fancier ones 🙂

Cisco and Trend

Not sure when Cisco decided to work with Trend for content filtering. But I do not think it is working as (at least) I expected. One good thing though is licensing works as 1-Click.

To show and register for the Content Filtering on Cisco 1920 router:

Router#sh ip trm subscription status
Router#trm register