Questions tagged [troubleshooting]

For questions requiring troubleshooting assistance with persistent/unresolved problems.

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Mux RAD4104, alarm led is red, but alarm log is empty

Cant turn off the alarm LED on my RAD4104 multiplexer. show active alarms is all zero. show alarm-log is empty. Any suggestion, please?
0 votes
1 answer
70 views

How to determine if a network cable is bad on a LAN under an unmanaged switch with no DHCP?

Is there anyway to detect this via automation and software? I know if I can get access to the MAC address table on the switch I can see if there's a missing MAC address. I don't know if this is ...
14 votes
1 answer
6k views

Troubleshooting low Metro Ethernet TCP throughput

Background We rented a few layer 2 leased lines, i.e. you have one big pipe at the datacenter and the remote sites have smaller pipes. Inside the layer 2 network you can do whatever you like. Probably ...
14 votes
3 answers
65k 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: ...
0 votes
0 answers
121 views

Eigrp flapping while using natting with route map

I have configured a topology which contains ip sla , route map , dual natting.It work perfect but when I used route map natting the eigrp become flapping and show the error is "retry limit ...
0 votes
0 answers
22 views

Cisco Kron Job starts later and later

I use a Kron job to ring a shit bell for our manufacturing plant. The application works, but the job starts 35+ seconds late. The problem seems to be getting worse, a few days ago it was at 35 secs ...
1 vote
2 answers
1k views

Poor bandwidth after re-coupling an Ethernet cable

As part of an experiment I cut a Cat 5e Ethernet cable in half, stripped off a small amount of insulation on each wire and attached each pair of wires together with its own alligator clip. There are ...
0 votes
0 answers
297 views

NAT overload and access to web resources

I have really bizarre problem in clients network. Clients have access to the internet via NAPT - I'm using several public ip addreses for this purpose. (I'll change ip addresses for obv reasons) ip ...
2 votes
3 answers
810 views

How can you determine the result of a load-balancing hashing algorithm (such as ECMP/LAG) for troubleshooting?

In many architectures there are load-balancing mechanisms such as ECMP routing or LAG between various interfaces. This load-balancing is usually per-flow, based on a hash of various criteria, such as ...
0 votes
2 answers
591 views

Do I have to reboot the Fortigate 1000c after modification on static route?

I am using a Fortigate 1000c working on NAT mode. It has two WAN connections (WAN1 and WAN2). I am using a static route. For some reasons, There are many firewalls and routers (Cisco, TP-Link and so.....
4 votes
2 answers
368 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'...
-2 votes
1 answer
89 views

Does the bandwidth of a Comcast modem divide if it is connected to two routers on two subnets? [closed]

I have a 150 megabits/sec Comcast pipe that connects to two subnets through two Cisco routers. The bandwidth at the modem is 150 Mb/s. The bandwidth at one router is 96 Mb/s and the other is 96 Mb/s ...
0 votes
1 answer
195 views

Does Telnet need to be activated on both devices I am using or not? [closed]

I've searched everywhere for the answer to this question but can't find a simple yes or no. Basically, I have a virtual server hosting some services and then a physical panel PC in another part of the ...
1 vote
2 answers
55 views

Steps on troubleshooting a network

If I have to troubleshoot a network stating that one of the interface is not working (i.e, a link is down), what steps would I need to take to make it working again?
17 votes
3 answers
100k 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 ...
3 votes
3 answers
4k views

MTR packet Loss at intermediate hop

We are currently having issues with our WebService being intermittently inaccessible to clients. During diagnosis with the NOC and with some internal testing we believe we have a router dropping ...
2 votes
2 answers
278 views

Cisco CoreSwitch 6509 Vlan connection problems

just wanted to ask what measures I'll have to do regarding on my problem on CoreSwitch 6509. I have 12 vlans on layer 3 switch which has 48 ports, 4 ports per vlan and I have a backbone on vlan 10 and ...
5 votes
2 answers
105 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 ...
24 votes
10 answers
309k 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?
11 votes
4 answers
50k 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....
5 votes
4 answers
9k 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 ...
6 votes
1 answer
858 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 ...
2 votes
0 answers
1k views

Point to Point ICMP Ping Loss between Juniper MX routers

I am facing problem with regard to 1 x 10G link (which is actually configured as an aggregated Ethernet (ae) i.e ae link contains only single 10G link. This ae link is connected between 2 x Juniper ...
2 votes
1 answer
55 views

How do I find out which NAT is getting hit?

I can see in packet captures that my packet's destination IP is getting translated. How do I find which NAT statement is responsible for the conversion if my device has over 200 NAT rules? I'm using ...
1 vote
1 answer
958 views

Cisco 49XX multicast flooding

I have problem with multicast on cisco 4948. I've got vlan 9 with muilticast, which configured on several ports. Switch floods multicast traffic on all ports configured with vlan 9. It consumes link ...
3 votes
1 answer
1k 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 ...
0 votes
1 answer
4k views

How to Troubleshoot Network Latency Step by Step

Does anyone have an idea of how to troubleshoot high network latency step by step? For example, let's say we have a remote office. And all users are from that office are having high latency accessing ...
3 votes
1 answer
1k 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. ...
2 votes
1 answer
1k views

Intermittent periods of high packet loss, one hop beyond router

I've been trying to diagnose internet connection issues at a remote small business for which I am the system administrator. If this is not the proper Stack Exchange to post to, I'd really appreciate ...
2 votes
3 answers
30k views

Output drops/errors on Cisco 3850

Sorry if this is a noob-ish question, but I am a bit lost. We are currently having some network issues, that seem to be manifesting in what appear to me to be odd ways. End result is I have some ...
2 votes
1 answer
3k views

continues to execute the command ping

tell me please why continues to execute the command ping... Router#ping vrf vrf-trust 50.50.50.50 sou 2.2.2.2 Type escape sequence to abort. ending 5, 100-byte ICMP Echos to 50.50.50.50, timeout is ...
1 vote
2 answers
403 views

What can I infer about a network connection using a cable tester (if anything)

I have a NS-468 cable tester for testing cables. This works fine but if I connect just one end of a RJ45 cable to a network, I only get 4 lights. This seems reasonable as I suppose 4 pins are for ...
2 votes
1 answer
138 views

Routing and Switching & network monitoring

hi i am facing problem in juniper switch Model: ex4200-48t ,Junos: 15.1R6.7 . i deploy network monitoring check-MK software. there is showing errors of juniper switch ports and also show in logs file ...
1 vote
0 answers
33 views

Troubleshooting slow connections in large data centers [closed]

I’ve been asked this question - or a variation of it - during some recente job interviews. I think my answers were adequate (involving reducing scope, packet tracer with many probes, etc) but I’m ...
1 vote
0 answers
73 views

Internet not working [closed]

I have this types of network in my office. Recently we have moved to new i BSNL internet. My problem is when i bypass router and connect poe cable to computer internet is working but when i put ...
1 vote
1 answer
459 views

Cisco: Router can ping Internet, Clients cannot

I'm currently playing around with a Cisco 819 LTE-integrated (C819G-4G-G-K9) router at my summer place to get a better LTE-signal and control that the ISP router provides me. Currently I'm stuck at ...
3 votes
1 answer
512 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 ...
6 votes
2 answers
3k 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 ...
8 votes
1 answer
2k 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. ...
4 votes
1 answer
419 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 ...
0 votes
1 answer
43 views

Mixed Use Four-pair Cable

My school tried to save money, so they decide to use an installed cable for phone, CCTV, and ethernet. I used two pairs for ethernet, one for phone, and one for a CCTV camera. The phone and camera ...
1 vote
2 answers
131 views

Cat 5e wiring Type A incompatibility with Type B

I am not an engineer but I’m having problems with my small network in my business. I have 11 computers after 13 yrs am having major problems. My network keeps shutting down, and my dental software on ...
1 vote
2 answers
275 views

Cisco 1800 series: sys-2-chunkexpanfail: error every time

My knowledge of Cisco is very basic and I´m having this error constantly. I have to reboot every time, and it does not seem right. How can I solve it at once?? What I know of this device is that it ...
2 votes
1 answer
744 views

arp or proxy-arp causing high cpu

We have an issue on a Cisco A901-6CZ-F-A with high cpu caused by Arp requests coming on Vlan11 from our customer. We enabled 'debug arp' to try and diagnose, below is a small snippet. IP addresses ...
0 votes
1 answer
76 views

What are the "next steps" to take when business Internet service stops working? [closed]

Scenario (based on real events) a small business has a "BigCorp" Internet service. One day the Internet goes down after a power outage, and they call BigCorp for help. BigCorp support over the phone ...
6 votes
1 answer
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 ...
2 votes
1 answer
69 views

Different responses IP and domain name [closed]

I have a domain name that is using a public IP, when I send two requests, one to the domain name and one to the IP I get different headers in each one, in one of them 4 cookies are set, in the other ...
3 votes
1 answer
6k views

Ping sometimes works and sometimes fails [closed]

I have a Cloud Core Router with v6.1 RouterOs. It has defined a PPPoE client, add-default-route to yes and masquerade to out interface. I can ping the router from any device connected to the internet ...
4 votes
4 answers
425 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 } ...
0 votes
1 answer
2k views

Can't connect to FTP [closed]

I am using Beetel 777VR1 with Airtel Broadband. I am trying to connect with a FTP server but I am not able to access that. However with same credentials when I try to connect with my mobile ...