Posted by: Mar Apuhin | June 25, 2009

Cisco’s Command Output Interpreter

I have a customer that is complaining a lot of CRC and input errors on the interface.
This has been diagnosed with the help of Cisco's Output Interpreter.

R1#sh int s0/0/0
Serial0/0/0 is up, line protocol is up
 Hardware is GT96K Serial
 Description: R1
 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
 reliability 255/255, txload 39/255, rxload 38/255
 Encapsulation FRAME-RELAY IETF, loopback not set
 Keepalive set (10 sec)
 Carrier delay is 15 sec
 LMI enq sent  1146, LMI stat recvd 1146, LMI upd recvd 0, DTE LMI up
 LMI enq recvd 0, LMI stat sent  0, LMI upd sent  0
 LMI DLCI 1023  LMI type is CISCO  frame relay DTE
 FR SVC disabled, LAPF state down
 Broadcast queue 0/64, broadcasts sent/dropped 603/0, interface broadcasts 412
 Last input 00:00:00, output 00:00:00, output hang never
 Last clearing of "show interface" counters 03:10:56
 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 751448
 Queueing strategy: weighted fair
 Output queue: 63/1000/64/751448 (size/max total/threshold/drops)
 Conversations  1/3/256 (active/max active/max total)
 Reserved Conversations 0/0 (allocated/max allocated)
 Available Bandwidth 1158 kilobits/sec
 5 minute input rate 235000 bits/sec, 22 packets/sec
 5 minute output rate 237000 bits/sec, 21 packets/sec
 34006 packets input, 39923277 bytes, 0 no buffer
 Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
 4 input errors, 4 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
 38081 packets output, 42136153 bytes, 0 underruns
 0 output errors, 0 collisions, 0 interface resets
 0 output buffer failures, 0 output buffers swapped out
 0 carrier transitions
 DCD=up  DSR=up  DTR=up  RTS=up  CTS=up
R1#

If you paste this on the CISCO OUTPUT Interpreter you would get the following:

SHOW INTERFACE SERIAL NOTIFICATIONS (if any)

Interface Serial0/0/0 (up/up)
  WARNING: The counters for this interface have not been cleared for 3 hours 10
  minutes 56 seconds.
  TRY THIS: Use the 'clear counters Serial0/0/0' command to ensure current information
  is being displayed. This will assist when troubleshooting serial interface issues.

  WARNING: This interface has a high number of output drops.
  The input rate to this interface has exceeded the bandwidth available on the
  serial link.
  TRY THIS:
  1. Minimize periodic broadcast traffic like routing and Service Advertising
     Protocol (SAP) updates (if applicable) by using access lists or by other
     means.
  2. Turn off fast switching for heavily used protocols. For example, turn off
     IP fast switching by using the 'no ip route-cache' interface configuration
     command.
  3. Implement priority queuing on slower serial links.
  4. Submit the output from 'show buffers' to Output Interpreter to determine
     if buffers need to be tuned.
  REFERENCE: For more information see: Troubleshooting Output Drops

  WARNING: This interface has received a high number (0.01176% of input packets)
  of packets with incorrect CRCs (corrupted data).
  Problems that may cause this symptom include:
  a. Noisy serial line
  b. Serial cable is too long or cable from the CSU/DSU to the router is not
     shielded
  c. SCTE mode is not enabled on the DSU
  d. The CSU line clock is incorrectly configured
  e. A Ones density problem on the link (incorrect framing or coding
     specification), exists
  f. Verify the queuing strategies are the same on both ends of the link.
  TRY THIS:
  1. Ensure that the line is clean enough for transmission requirements. Shield
     the cable if necessary.
  2. Make sure the cable is within the recommended length (no more than 50 feet
     [15.24 meters], or 25 feet [7.62 meters] for the link).
  3. Ensure that all devices are properly configured for a common line clock.
     Set serial clock transmit external (SCTE) on the local and remote DSU. If
     you are attempting serial connections at speeds greater than 64 kbps with
     a CSU/DSU that does not support (SCTE), you might have to invert the
     transmit clock on the router. Inverting the transmit clock compensates
     for phase-shifts between the data and clock signals.
  4. Make certain that the local and remote CSU/DSU are configured for the
     same framing and coding scheme as that used by the leased-line or other
     carrier service (for example, ESF/B8ZS).
  5. Contact your leased-line or other carrier service and have them perform
     integrity tests on the line.

REFERENCE: For more information on Serial Lines, see:
  Troubleshooting Serial Line Problems
  Configuring Serial Interfaces
  Troubleshooting Serial Lines
  Loopback Tests for T1/56K Lines

REFERENCE: For more information on Frame-Relay, see:
  Frame Relay
  Configuring Frame Relay
  Configuring and Troubleshooting Frame Relay
  Configuring and Troubleshooting Frame Relay Broadcase Queue
  Troubleshooting Frame Relay Networks
SHOW INTERFACE SERIAL NOTIFICATIONS (if any) Interface Serial0/0/0 (up/up) WARNING: The counters for this interface have not been cleared for 3 hours 10 minutes 56 seconds. TRY THIS: Use the ‘clear counters Serial0/0/0′ command to ensure current information is being displayed. This will assist when troubleshooting serial interface issues. WARNING: This interface has a high number of output drops. The input rate to this interface has exceeded the bandwidth available on the serial link. TRY THIS: 1. Minimize periodic broadcast traffic like routing and Service Advertising Protocol (SAP) updates (if applicable) by using access lists or by other means. 2. Turn off fast switching for heavily used protocols. For example, turn off IP fast switching by using the ‘no ip route-cache’ interface configuration command. 3. Implement priority queuing on slower serial links. 4. Submit the output from ’show buffers’ to Output Interpreter to determine if buffers need to be tuned. REFERENCE: For more information see: Troubleshooting Output Drops WARNING: This interface has received a high number (0.01176% of input packets) of packets with incorrect CRCs (corrupted data). Problems that may cause this symptom include: a. Noisy serial line b. Serial cable is too long or cable from the CSU/DSU to the router is not shielded c. SCTE mode is not enabled on the DSU d. The CSU line clock is incorrectly configured e. A Ones density problem on the link (incorrect framing or coding specification), exists f. Verify the queuing strategies are the same on both ends of the link. TRY THIS: 1. Ensure that the line is clean enough for transmission requirements. Shield the cable if necessary. 2. Make sure the cable is within the recommended length (no more than 50 feet [15.24 meters], or 25 feet [7.62 meters] for the link). 3. Ensure that all devices are properly configured for a common line clock. Set serial clock transmit external (SCTE) on the local and remote DSU. If you are attempting serial connections at speeds greater than 64 kbps with a CSU/DSU that does not support (SCTE), you might have to invert the transmit clock on the router. Inverting the transmit clock compensates for phase-shifts between the data and clock signals. 4. Make certain that the local and remote CSU/DSU are configured for the same framing and coding scheme as that used by the leased-line or other carrier service (for example, ESF/B8ZS). 5. Contact your leased-line or other carrier service and have them perform integrity tests on the line. REFERENCE: For more information on Serial Lines, see: Troubleshooting Serial Line Problems Configuring Serial Interfaces Troubleshooting Serial Lines Loopback Tests for T1/56K Lines REFERENCE: For more information on Frame-Relay, see: Frame Relay Configuring Frame Relay Configuring and Troubleshooting Frame Relay Configuring and Troubleshooting Frame Relay Broadcase Queue Troubleshooting Frame Relay Networks
Posted by: Mar Apuhin | May 24, 2009

My 27 Favorite Aliases

conf t
alias exec r show ip route
alias exec ss show run | s ^router
alias exec sr show run | b ^router
alias exec s show ip int brief
alias exec su show ip int brief | e unassigned

alias exec r6 show ipv6 route
alias exec s6 show ipv6 int brief
alias exec rc show run
alias exec i show run interface
alias exec b show ip bgp

alias exec o show ip ospf
alias exec e shwo ip eigrp
alias exec c config term
alias exec pm show policy-map
alias exec rm show route-map

alias exec al show access-list
alias exec pl show ip prefix-list
alias exec m show ip mroute
alias exec pp show ip pim
alias exec cm show class-map

alias exec v show vlan brief
alias exec pb ping 255.255.255.255
alias exec ciop clear ip ospf proce
alias exec cien clear ip eigrp nei
alias exec cib clear ip bgp *

alias exec cir clear ip route *
alias exec t show int trunk
end
wr

Posted by: Mar Apuhin | May 14, 2009

How to summarize IPV6 address in a quick way?

Remember that IPv6 is composed of 128 bits. This is commonly expressed by 16’s in 8 groups (8 * 16 = 128).
Example IPv6 address: FEC0:0:0:A:125:23FF:FEE2:1F53 (count the “:” it is a group by 8)

Summarization Tidbits:

Example:

Summarize the following addresses:
FEC0:0:0:A:125:23FF:FEE2:1F53 and
FEC0:0:0:E:10A:9FFF:FED7:D3

0000 0000 0000 1010 – A
0000 0000 0000 1110 – E
0000 0000 0000 1000 – 8 – common mask

FEC0 + 0 + 0 = 48 bit position
16 + 16 + 16 = 48,

+ (12 zeros common between A and E, as per above)
48 + 12 = 60

+ (1 bit for the 8 – common mask)
60 + 1 = 61  <—total bit position, this is your MASK.

Answer: FEC0:0:0:8::/61

Gets?

Posted by: Mar Apuhin | May 9, 2009

Cisco Revising CCIE R&S Certification

The upcoming Version 4.0 of Cisco CCIE® Routing and Switching certification will test hands-on troubleshooting, Multiprotocol Label Switching (MPLS), and VPN networking.

To reflect the growth of the network as a service platform, Cisco is revising the certification requirements for CCIE Routing & Switching (CCIE R&S)–the expert level certification for network engineers. The new requirements were developed with assistance from Cisco enterprise customers and reflect the expectations of employers across industries.

The competencies required for CCIE R&S v4.0 certification were released on May 5, 2009, and are available on the Cisco Learning Network under the CCIE R&S v4.0 Written Exam topics and CCIE R&S v4.0 Lab Exam topics. Exams based on the new requirements are scheduled for release on October 18, 2009, and will immediately replace the currently available v3.0 exams. Candidates who plan to take their exams on October 18, 2009, or later should prepare using the new v4.0 exam topics.

Both the written and lab exams will be refreshed with new questions and will cover MPLS and VPN networking. The written exam will add scenario-based questions to the multiple choice questions, and the lab will now require hands-on troubleshooting of preconfigured networks, in addition to configuration. Exam duration and pricing will remain the same, with the two-hour written exam at USD$350 and the eight-hour lab at USD$1400. A beta version of the new CCIE R&S v4.0 written exam (351-001) will be available to all customers in the July–August 2009 timeframe at a discounted price of USD$50. An announcement will be made when scheduling begins.

https://cisco.hosted.jivesoftware.com/docs/DOC-4605

What Cisco proprietary STP feature configured in a switch prevents it from becoming a transit node under most circumstances? 
Answer (Highlight to answer):  Uplink-Fast

Q5. Accoring to RFC specifications, what is the exact Administratively Scope Multicast address used in common/real practice?

Answer (Highlight to answer):  239.15.0.0/16 (but for CCIE exam its is 239.0.0.0/8)

Q4. IGMP packets are designated by which IP protocol number?

Answer (Highlight to answer): 2 (two)

Q3. The member ports of a switch’s local EtherChannel are set to on. In order to successfully form an Which PIM forwarding mode uses a flood and prune method, with a 3 minute cycle?

Answer (Highlight to answer): PIM dense-mode

Q2. The member ports of a switch’s local EtherChannel are set to “on”. In order to successfully form an EtherChannel link, the remote switch’ member ports should be set to what mode?

Answer (Highlight to answer): Mode “On”

I am posting 1-2 question(s) of the for the CCIE RS core knowledge exam every day. This will be short and brief, can be answered is few words. I will call it “banner qotd”.

banner qotd – New CISCO IOS command. ( -:).

Q1. In EIGRP, it uses a multicast flow timer and a retransmission timeout to control the Reliable Transport Protocol. What is the average elapse time, measured in milliseconds (ms), between the transmission of  a packet and the receipt of the acknowledgment?

Answer (Highlight to answer):  SRTT (smooth round trip time)


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