Questions tagged [troubleshooting]

For questions requiring troubleshooting assistance with persistent/unresolved problems.

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28
votes
2answers
48k views

What is the meaning of the CRC counter on a cisco device?

If the CRC counter of an interface is high, normally it's a bad sign, but why? If the count is high, what does this mean technically? What can cause this counter to go up? On which layer in the OSI ...
24
votes
10answers
245k views

How to find the port a device is connected to, based on IP, on a Cisco Catalyst switch

On a Cisco Catalyst switch, I need to find what port an end device is connected to. I have the IP address/host name. How do I quickly find the port?
16
votes
3answers
10k views

mtr output with high packet loss on one hop

I'm investigating a complaint of poor performance from an end user accessing a site I help maintain. I have these two mtr outputs to the end user, the first from the site: ...
14
votes
2answers
6k views

Troubleshooting low Metro Ethernet TCP throughput

The setup We have rented a few leased lines that present themselves as a layer 2 network, i.e. you have one big pipe at the datacenter and the remote sites have smaller pipes. Inside the layer 2 ...
13
votes
3answers
64k views

What is the meaning of RSSI?

When using mobile 3G routers, you see in the output of the "show cellullar 0 all" command. What is the significance of this value? Is this interpretation the same when talking about 2G or 3G? Ex: ...
13
votes
3answers
57k views

How to verify that a UDP port is open? [closed]

I have here a dilemma. I have a device that communicates to another remote device but there is a firewall between them. It's a UDP connection, so TCP utilities don't work to test if the specific port ...
11
votes
4answers
34k views

Interpreting TTL in ping results

I work for a VoIP service provider and I am working an issue with a customer who has a cable internet connection that's throwing me for a loop. He has a single block, which we'll pretend is 70.141.15....
9
votes
5answers
10k views

Monitor specific traffic type on a Cisco router

Is it possible to monitor a specific traffic type going through a cisco router? (like monitoring via wireshark) Ex: I want to monitor http traffic specifically that is passing through a router. (or ...
9
votes
4answers
366 views

Recording latency between a controlled startpoint and uncontrolled endpoint

This might be a very basic troubleshooting question, but it's worth asking to make sure I'm testing things the correct way and interpreting results effectively. I have a controlled start point (a ...
9
votes
1answer
2k views

Prefixes with aggregate labels not fully tracerouting across MPLS core

I have two routers, A (Cat6500 w/SUP720-3BXL, IOS 12.2(33)SXH4) and B (Nexus 7K w/SUP1, NX-OS 5.2(4)), separated by several hops across an MPLS core, each with VRF ABC. Router A has two directly ...
9
votes
1answer
13k views

ProCurve CPU at 100% for several minutes after reboot

I have been doing firmware upgrades in HP switches. Two different models have been upgraded: ProCurve Switch 5406zl Intelligent Edge (J8697A): upgraded from K.15.06.0008 to K.15.12.0012 HP 2520-24G-...
9
votes
1answer
2k views

Strange drop-outs in Cisco 7200 LNS lab

I'm testing several functions on emulated Cisco 7200 routers, in GNS3, prior to actual purchase. One of the functions I've been testing out is LNS functionality. I've been primarily following this ...
8
votes
1answer
1k views

ASA5550 Error: assertion “_vf_mode_init” failed: file “vf_api.c”, line 99

I pulled an old ASA5550 off the shelf, which had 8.4(2) loaded on it. When I tried to boot it, I got the following error... ----------------------------------------------- Traceback output aborted. ...
8
votes
1answer
4k views

Unpredictable Juniper SNMPv3 Access Error

We're having issues where SNMPv3 ceases to accept SNMP requests on our Juniper EX series switches. In what seems like random occurrences, Juniper nodes refuse SNMP authentication credentials. This ...
8
votes
4answers
2k views

Internal BGP route exchange issue

I have BGP multihoming with two cisco routers. Each router has its own ISP and announce our AS with our /24 network to the internet. My issue is between those two routers : Router A, routing table ...
7
votes
3answers
5k views

Edit Cisco IOS ACL without hanging the router

I have a Cisco Router 1941 Series and I want to make some changes to the access-list on the router. I got to know I will have to delete one of the list and then re-add everything again with my ...
7
votes
1answer
25k views

Configuring a Cisco ASA 5505 for routing

I'll start by pointig out that networking issues have always left me scratching my head. There is something about routing especially that I just haven't had that "Oh I get it" moment yet, so it's ...
7
votes
1answer
3k views

Cisco ISE backup shows as success but no data was written to backup server

I'm trying to back up a Cisco ISE server (version 1.2.0.899 patch 4) via sftp. I configuered a repo via the web gui. I added the hostkey (for the backup server) via the command line. I make sure the ...
7
votes
2answers
611 views

OSPF on ASA 8.2 not advertising /32

We have set up OSPF between our 2 ASA 5540 running in Active/Passive and our Internet provider's Juniper routers. We would like to advertise routes based on the content of an ACL through a route-map : ...
6
votes
1answer
3k views

VPN Connection: Can ping printer but not server what is blocking things?

I have a VPN set up between several offices. All but one work fine. With one office, I can ping the printer 192.168.45.30 but not a server 192.168.45.242. Well, I say I can't but when the server was ...
6
votes
1answer
421 views

Bandwidth limit Cisco 3400 ME problem

I want to limit bandwidth (speed) of interface of Cisco 3400 ME switch. I did these: policy-map parent class class-default shape average 64000 And in gi0/2 interface I apply it: service-policy ...
6
votes
1answer
3k views

Cisco + FreeRADIUS: Exec 15 level privilege mode

I have two routers: Cisco ISR 2921 with IOS version 15.0(1r)M9 and a Cisco C2600 which is an old guy with IOS 12.0(7)XK1. I have this set up on a FreeRADIUS server: router-admin MD5-Password := "&...
6
votes
4answers
16k views

How do I pinpoint bandwidth consumers on my Fortigate?

For a long time now we've been having huge connection problems at work. The Internet connection is bad, for sure, but I don't think they are the main problem, they don't see any packet loss on their ...
6
votes
1answer
2k views

How do I create an SSL CSR via CLI for Cisco Prime?

I'm trying to create a csr for a cisco prime server. I managed to create a csr and put it in the "defaultRepo", which is local on the disk. After what I've read I need to create a certificate repo ...
6
votes
1answer
1k views

Split Horizon will not disable on interface

I'm trying to set up a DMVPN Phase 2 configuration, but I cannot manage to get past Phase 1 because the hub router's tunnel interface refuses to disable split-horizon. The spokes never form an EIGRP ...
6
votes
1answer
2k views

SRX100 in bootloop. Flash storage problem?

About a month ago one of my SRX100 started to go into a bootloop for no obvious reason to me. After some hours, it eventually stopped and booted up the system again (primary) and I was happy that I ...
6
votes
2answers
5k views

Juniper EX2200 can't boot

I recently acquired a Juniper EX2200-24T-4G switch, but I have some issues getting it up and running. When I power on the switch the boot process looks normal, but after some time it suddenly turns ...
6
votes
1answer
553 views

WIPS Alert: Reason “NoProfile” detected on AP

I'm trying to understand how I should act on a trap I'm receiving from our WLC WIPS Alert: Reason "NoProfile" detected on AP MAC: 00:1a:30:00:00:00, AP Name: West128_c3602i My searches for the ...
6
votes
1answer
362 views

Odd stp issue on foundrys

I have 2 foundry devices running 802.1w which are both connected to an access switch which also runs 802.1w. The 2 foundry's are connected to each as well. I have the vlan configured on each of the ...
6
votes
1answer
913 views

7609 + SIP-400 PPPoE: cannot route to the Internet

I am trying to configure a 7609 router with a SUP7203BXL, SIP-400 and SPA5xGE as BRAS. The configuration is at the bottom of the question. The sessions are created, but the clients can't reach ...
6
votes
2answers
11k views

Cisco 6509 Supervisor Card Slot Boot Failure

We recently had a sporadic reboot of a distribution switch for an unknown reason. No recent hardware/software changes have been made. Our log files don't indicate anything leading up to the incident. ...
5
votes
4answers
5k views

DLink switch loses configuration on power off!

We just bought a DGS-1210-28P smart switch, it is my first experience with a business class switch, however I found a pretty weird behavior. The switch loses all of its configurations, even management ...
5
votes
2answers
31k views

Troubleshooting “TCP Zero Window” Issues

I'm currently having a problem troubleshooting a trading application. Let me give a simple diagram of the current network setup (Gov't Stock Exchange Network Router)X-->(256kbs Leased Line)<--X(...
5
votes
2answers
70 views

Cisco 2821 hangs with “No memory”

I have one (pretty old) 2821 router, running BGP with 2 ISPs. (C2800NM-ADVENTERPRISEK9_IVS_LI-M), Version 12.4(24)T5 Sometimes for unknown reason it just hangs, and as it is remote location I cannot ...
5
votes
1answer
412 views

Force fraffic between PPPoE users to pass through traffic management device

I would like that traffic between pppoe users passes through a traffic management device as showed below I have evarything working, i mean, users have ppp session and they have internet access via a ...
5
votes
1answer
2k views

Cisco Aironet Last Activity Counter seems not to work causing clients to drop frequently

My current Setup: Two SSIDs broadcasted SSID 1 (airlan) is configured with dot1X and dynamic vlan association SSID 2 (prv) with PSK and a static vlan I've recognized, that every 60s the devices on ...
4
votes
2answers
2k views

What is an acceptable spell of total packet loss for public Internet traffic?

The context: an Internet facing web site, streaming near real-time market prices. Paying customers can be anywhere on the Internet. The issue: Customers can experience total packet loss for 10s, 30s ...
4
votes
4answers
2k views

CPU Impact of “debug ip packet” on Cisco Switches

in terms of CPU consumption and possible traffic disruption, what should I generally expect when I run the command: Switch#debug ip packet on a Cisco device in a large ISP network? Cisco devices in ...
4
votes
1answer
2k views

CRC & Align Errors on D-Link switch, network down

I have network topology: (room 3) D-Link DES-1024D | | (room 2 MAIN) (room 4) Baseline 3COM Switch 2948-...
4
votes
1answer
157 views

PAT not translating at all

I am studying for my CCENT. I threw together a PAT practice lab. Other than DHCP and RIP everything is pretty stock. No VLANs No security Just NAT overload on ACCESS router. I am stumped why it isn'...
4
votes
3answers
517 views

How can I know about if there is a smurf attack on my network?

I have been having network issues. The users report to me problems with the internet, but actually the problem is on my network. I have a sonicwall firewall and the device logs indicate posible tcp ...
4
votes
2answers
6k views

Cisco ISE - Issues after new CA Certificate

Our Root CA Certificate expired recently, in advance we loaded the new one on our ISE servers however after the expiry we have had issues with Android devices and BYOD onboarding. Apple devices are ...
4
votes
1answer
280 views

Latency in P2P Circuit

I have one P2P Circuit from our HQ to a secondary office. the distance between them is approx 2kms. Earlier when the Circuit was delivered at that time we were having an RTT of 3-4ms. It is a 10Mbps ...
4
votes
2answers
686 views

Multiple error types Cisco 861 router

I have a connection that users complain is really slow at times. My SNMP graphs from Observium don't show the bandwidth being fully used or high latency. They show a lot of errors on the WAN port of ...
4
votes
1answer
1k views

How to troubleshoot reason why ARP replies from ISP are not forwarded through our switch?

At one of our offices, a new ISP recently installed an Internet connection via Radwin microwave radios, going to an E1 line back to the capital where their routing equipment is. There is a very ...
4
votes
1answer
6k views

ASA 5510 NAT stops working

I’ve been searching on this issue and can’t seem to find info about it. I’ve inherited an older ASA5510 (8.2(1)) and unfortunately I’m pretty new to them. I have a set of overloaded NAT statements ...
4
votes
4answers
396 views

How do I fix my vlans connection to the Internet?

I have the following abridged configuration for a Ubiquiti switch: interfaces { ethernet eth1 { address 192.168.4.1/24 vif 101 { address 10.10.254.1/24 } ...
3
votes
1answer
352 views

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. ...
3
votes
1answer
471 views

Problem with IP phones after ISP failover change

I've ran into a strange problem at one of my clients. They use ShoreTel Sky cloud IP telephony service and use Cisco 7960 IP phones hooked up to an ASA 5520. The configuration is done through IP SLA ...
3
votes
1answer
91 views

Cisco Router IOS update

I am facing problem in update the IOS of Cisco 7304 router. I am upgrading from 12.4(24)T2, to 15.2(4)S7 this. but I was boot from this version 15.2(4)S7 it booted proper from flash. But when I put ...