Questions tagged [router]

For questions about network routers, devices that forward data packets between computer networks, commonly at the network layer (layer 3) of the OSI model.

Filter by
Sorted by
Tagged with
6
votes
2answers
26k views

What are the different modes in Cisco routers, and why these modes?

I want to know on what basis Cisco designed the different modes in their routers. For example: config mode execution mode Can any one give the perfect reasons behind the different modes? What ...
5
votes
4answers
17k views

Multiple sub-nets behind a router

I have 3 simple questions:- Is is possible to have multiple subnets behind a router? I believe it is, e.g. router LAN interface would have subnet mask 255.255.0.0 and machines connecting to the ...
4
votes
1answer
7k views

Cisco show all static route

Here is the question -> I have added a floating static route with administrative distance 200 to a router, as default, show ip route static only displays one static route with the lowest ...
6
votes
1answer
293 views

CISCO developer routers/ firmware

I was wandering if there are any CISCO routers and firmware for purchase or download for developers so I could test my implementations on them. I am developing a firmware plugin to increase security ...
0
votes
2answers
9k views

Configure a Guest network on a Sonicwall TZ-205 N

I'm trying to configure a Sonicwall TZ-205 N to have 2 wireless networks. The first wireless network is a guest network which only has access to the internet (client isolation would be nice but is not ...
8
votes
1answer
2k views

Something is filling my force10 ARP table

I have 2 force10 s25 switches that are used for a dark fiber link between two school buildings. One of my switches is filling its ARP table to the brim and then failing. This can happen as often as ...
14
votes
2answers
1k views

BGP regular expression .+_.+_.+_.+_.+_.+_.+_.+_.+_.+_.+_.+

could anyone tell me what ip as-path access-list 100 deny .+_.+_.+_.+_.+_.+_.+_.+_.+_.+_.+_.+ stands for?! I searched over the internet for the meaning of this regular expression, but I was unable to ...
4
votes
2answers
4k views

AODV sequence numbers and loop prevention

I am learning about the AODV (ad-hoc on-demand distance vector) protocol. I saw a "sequence number" with a value like "A 46"; however, I don't understand why incrementing this sequence number can ...
4
votes
3answers
270 views

Router neighbour config discovery

I am new to the whole networking world and I apologize if this is a re-post of a question. What I want to know is that is there a mechanism for routers to discover its environment. NOT what a ...
16
votes
3answers
3k views

class-default matches control traffic?

I'm seeing an issue with BFD on a link that's being policed egress where it appears during times where the policer is maxed BFD packets are not getting to the other side. I'm wondering if BFD hellos ...
12
votes
2answers
10k views

Error: `EIGRP is restricted to stub configurations only on this platform`

We just bought some new Cat4507R+E distribution switches. When we bought the switches, we asked for an Advanced Services K9 image, but our reseller told us they only come with a Universal K9 image. ...
5
votes
3answers
270 views

Are VPN Routers the same as a Router

I'm currently looking at the Cisco RV042 VPN router, and I am wondering if I will be able to setup individual networks with it. How do I know which routers or firewalls are capable of setting up ...
6
votes
1answer
185 views

Cisco 3620, installing nm-2fe2w

Is the WIC plug and play or are there commands that I need to run? The router is not showing the interfaces. I tried using the sh diag and it didn't show anything.
4
votes
2answers
4k views

cisco 877 router QoS on traffic with a specific destination

Is it possible to throttle traffic coming or going to a specific ip address on a cisco 877 running : C870-ADVIPSERVICESK9-M, 12.4(15)T12, RELEASE SOFTWARE (fc3)? Background: we have a WAN where ...
8
votes
3answers
4k views

slot vs sub-slot?

I am trying to understand how Cisco interfaces are named, so I am reading the document Interface and Line Numbers in Cisco 1800, 2800 and 3800 Series Routers I am having some issues understanding the ...
5
votes
6answers
608 views

Can the same network IPs be used more than once

Because of how routers separate networks is it possible to say use the network 192.168.1.0/24 several times as long as you have enough networks to separate? Example: 192.168.1.0/24 <--> 172.16.0....
10
votes
1answer
3k views

Long login delay when cisco device is booted

Whenever we boot or reboot a Cisco router or switch we have to wait a number of minutes before we can get a username prompt for login. We get a few fail messages Press RETURN to get started. % ...
4
votes
3answers
950 views

Can't connect to console on down Cisco 861 Router

I'm networking beginner I have a remote site without any servers and a Cisco 861 that has and IPsec VPN tunnel back to the main office. I get an alert that it's offline via a ping test. Yesterday ...
12
votes
3answers
11k views

OSPF Stuck in Exstart Adjacency State

According to this article two routers will get stuck in the exstart adjacency state when their configured MTU sizes do not match. Does a VLAN tag affect this as well even if the routers involved are ...
3
votes
5answers
19k views

Routing Serial cables instead of Ethernet

I am doing some CCNA training videos and using packet tracer and they showed using a serial cable to connect two routers. Why are serial cables used instead of Ethernet cables? Does it depend on the ...
5
votes
2answers
2k views

Summarized route not being shared in EIGRP

Working through a lab for CCNP prep. Task is simple - create 4 loopback addresses on R3 - all 172.16.X.0/24 addresses, and share the routes to neighboring routers so that they appear as /22's instead....
17
votes
7answers
51k views

Cisco command to show which interfaces an ACL is applied to

For Cisco routers and switches, is there a show command, or something similar, that will display what physical and logical interfaces an ACL is implemented on and what direction it is applied in? I ...
7
votes
2answers
3k views

How to configure OOB access via IP

Single Cisco IOS device in a remote DC, I have an OOB connection delivered into the rack (length of Cat5e into my rack from another onsite providers rack, who have diverse routes from my own, in and ...
2
votes
2answers
2k views

loopback ip issue

So I have a weird issue. If I configure a /30 ip on an ethernet interface, for example 10.10.10.1/30 on Router1 and 10.10.10.2/30 on an ethernet interface on Router2, I can ping each other fine...no ...
1
vote
3answers
787 views

How to keep office LAN private from public WLAN [closed]

I handle the network at a small business; it's not my primary job but one that I am in charge of. My boss owns a house next to the office that he uses as a general meeting area and as a guest house ...
15
votes
2answers
8k views

BGP multipath with different ASNs feasible for production networks?

on Cisco (this command is hidden for some reason) #bgp bestpath as-path multipath-relax The default BGP behavior only installs only routes with exact the same AS_PATH into RIB. With multipath-relax, ...
10
votes
3answers
21k views

Using IP addresses from IP pool given by ISP

My ISP says that it can provide an optic fiber connection with a pool of 4 static IP addresses (subnet 255.255.255.248 i think). My question is that if I get that connection, 1 ip will be used for ...
11
votes
3answers
1k views

Do today's routers prevent fake IP headers?

I know people can modify the IP headers and change source IP address, but it should be simple for network devices to detect those messages. If they don't, why is it so hard? Does it add too much ...
13
votes
6answers
21k views

What happens when the ARP cache overflows?

In at least one implementation there is a hard limit on the capacity of the ARP table. What happens when the ARP cache is full and a packet is offered with a destination (or next-hop) that isn't ...
8
votes
3answers
1k views

DHCP Relay by MAC Address of CPE

We are testing a new Provisioning Server in DOCSIS/CMTS environment and we need to setup a lab with 5 models of CPE. I'm wondering if we can configure on Cisco Routers the dhcp relay (ip helper) ...
20
votes
2answers
25k views

Cause of high CPU load on Juniper peering router's routing engine

Recently the routing engine CPU utilization on two of our Juniper peering routers increased from ~10-20% average load to 80+%. I'm trying to figure out what's causing this (and how to get this high ...
16
votes
4answers
41k views

Bad Mask for IP Address Error

I'm not too clear on subnetting rules and experienced an error when I tried to assign 148.26.1.176/28 to an interface on my Cisco router. Can someone please explain why it was not allowing me to ...
8
votes
3answers
283 views

Is there a way to recognize the location where a client connects to the network?

So yes, I'm pretty new to networking and I hope this isn't a stupid question. I couldn't find an answer on google nor could I find something here (but I'm also sure about the terminology), so I ...
16
votes
3answers
9k views

Backing up Cisco router configuration - including ssh keys

We have some Cisco 2821, 2921 and 1921 routers in our shop. I can back up and restore the configurations by copying out or in the startup-config file, but what about the keys for ssh? I don't want ...
6
votes
2answers
1k views

forwarding / non forwarding Route Reflector?

I am considering running route reflectors in our current network topology of 20 od MX80's however all current devices are active traffic forwarders. from a scaling perspective RR makes logical sense ...
10
votes
4answers
4k views

how to get scp via snmp to work with cisco routers?

I have a lab setup where I'm trying to use SCP via SNMP to a cisco router.I found some online documentation such as: http://ccie20728.wordpress.com/2008/05/20/get-the-cisco-configuration-over-snmp/ ...
5
votes
1answer
129 views

ip-fwd-entry allocation fail OSPF

Any idea what this error means? I can't find much on googling. Device is a Brocade SX. Output is from: show ip ospf error **** Warning! ip-fwd-entry allocation fail 3629337 times --- The ...
8
votes
2answers
493 views

Determining optimal bandwidth needs for the office

We're currently using the Cisco 1921/K9 router along with SG300 L3 switch and other L2 switches in the office environment. We're hooked up to a 10M fiber line for internet but not sure if we need that ...
10
votes
4answers
5k views

Redundancy between router and servers

In the past, I was using a NetGear GS724T between my router and my servers. Unfortunatly the switch suddenly died. Now I've changed it for a GS748T and also bought one more and I am wondering how I ...
5
votes
3answers
3k views

Is a router always necessary to link two subnets?

I am thinking especially of VLANs, which represent separate subnets that may need only one switch.
9
votes
4answers
739 views

How does one specify certain IPs or MAC addresses for NBAR policy enforcement?

In an office environment, if I wanted to block youtube using a Cisco ISR router, I would set up the following with NBAR: class-map match-all YOUTUBE match protocol http host "*youtube.com*" ! policy-...
10
votes
4answers
16k views

Setting up DHCP server on the router or on the switch?

We're using the Cisco 1921/K9 with a SG300 L3 switch. Does one set up DHCP server on the router or on the SG300? If both is capable, what is the reason to choose one over the other? Note: I have 4 ...
11
votes
1answer
5k views

Cisco IOS built-in SSH client default version

You issue the command ssh 192.168.97.97 from a IOS device and the destination IOS router/switch SSH server is accepting both SSH versions. Being that you did not specify a version to use on the SSH ...
7
votes
3answers
3k views

ISR routers - difference between routed and switched ports

On a Cisco ISR router - would you say there are any benefits from purchasing an HWIC or EHWIC to connect to the next set of switches within the branch network? For instance. Lets say Gig0/0 and Gig0/...
10
votes
4answers
2k views

Embedded routers vs. software routers in the datacentre

I've been looking for a new 'core' router to put in our new rack which is colo'd at a nearby datacentre. What I've come across is the usual Cisco/Juniper/Brocade lineup, with the usual unattractive ...
12
votes
2answers
2k views

RIP routing is broken between two routers

There are 2 routers connected something like this: Network1 ----- (172.16.1.1/24) Router 1 (172.16.3.1/30) ------ (172.16.3.2/30) Router 2 ------ (172.16.2.1/24) Network 2 I try to add addresses for ...
16
votes
2answers
4k views

Output Drops on Serial interface: Better queueing or Output queue size?

On Internet edge routers speaking eBGP to multiple carriers and iBGP to one another, all interfaces on the LAN and WAN side are GE except for one Serial full-DS3 (~45Mbps) on each router. Although I ...
4
votes
2answers
3k views

OSPF LSA Refresh Time

Is there a Cisco command that would allow one to modify the default value of 1800 seconds (30 min) for the OSPF LSA refresh rate?
21
votes
7answers
7k views

Building new network and need 200+ wireless devices

I'm planning the network for my company's new office space. I'm not an expert so I'd like to present my plan and ask y'all nice folk to tell me if and where I'm making mistakes. Assumptions: Office ...
4
votes
4answers
2k views

Cisco 2600 series router logging a lot of “Memory allocation failed” errors

We are getting the below two error messages randomly on a 2600 series router. Syslog shows the router has been fine up until a few days ago. Would a reboot most likely cure the issue or is it most ...