generalnetworkerror
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What factors drive a Cisco IOS upgrade?
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26 votes

In order of preference/priority, our company tends to upgrade based on these factors: Vulnerabilities, vulnerabilities, vulnerabilities! Bugs Attaining new features not currently available-- new ...

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Reason for both a MAC and an IP address
26 votes

When you understand that IP-to-IP communication is really just a series of MAC-to-MAC communication taking place at each router hop, then you'll see why both are necessary. The IP header of a ...

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Cable Colors and Purpose
23 votes

Contrary to popular belief, there are cable color standards defined, just hardly anyone (myself included) follow them closely or at all. Check local jurisdictions for variants. ANSI/TIA/EIA-606-A ...

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Cisco - display ALL routes using a single command
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16 votes

show ip route vrf * displays the global routing table plus all the VRF instances. sh ip route vrf * 0.0.0.0 displays the default route for each VRF. This shows the default route for each VRF, ...

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What would cause really sporadic packet loss, when signal strength is fine
12 votes

Wireless video cameras cause about the worse interference. You don't need other 802.11 devices or access points to cause trouble as microwave ovens, some DECT phones, bluetooth, etc. can all run ...

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Why was the MTU size for ethernet frames calculated as 1500 bytes?
10 votes

When Ethernet was originally developed as a shared medium or bus with 10Base5 and 10Base2, collisions of frames were frequent (what else you would expect in a connection where you fork the signal by ...

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Bits per second vs. Packets per second
10 votes

Usually you are presented with throughput in Mbps (M-bits/sec) and Mpps (M-packets/sec). These are considered backplane or box throughput numbers. Marketing materials usually present the numbers in ...

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When to choose fiber instead of twisted pair (copper)
9 votes

One non-techncial reason to install fiber over copper for switch uplinks and the like, ignoring costs, etc: People are more afraid to touch a fiber cable compared to copper, so you'll get less of the ...

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SSH to Cisco ASA 5505
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8 votes

The ability to SSH to the firewall and ping outbound are usually two unrelated events and configuration. Since you're unable to ping the firewall's own 192.168.0.10 from itself, the interface appears ...

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Cisco IOS cli prompts - any way to know which interface you are configuring?
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7 votes

AFAIK, the answer is NO. I never understood how this valuable feature has escaped IOS for so many years or I manged to never discover it. ;-) I use the following technique in some cases when I want ...

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Dual ASA5510 with dual ISP failover
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7 votes

Assuming a single context active/passive failover configuration with the ASAs connecting to the 2911s on unique subnets, you could trunk the links using two subinterfaces and vlan tagging. But the ...

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Rogue RA what is this and how to counter it?
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7 votes

Router Advertisements (RAs) can provide autoconfiguration of default gateways for hosts instead of manually configuring each system. The downside is similar to the Rogue DHCP Server scenario: A Rogue ...

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Portforwarding by Subdomain
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7 votes

Without knowing much of your environment, you might want to look at Squid as a reverse proxy which can easily do what you seek. A reverse proxy is basically a load-balancer. No need to do anything ...

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F5 session timeouts
6 votes

For term sessions, I believe the best option is to use app or OS keepalives to maintain the connection through the SLB which allows you to keep your idle timeout where you want it. This is app and ...

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Is it possible to get a listing of all DNS records that have a given CNAME?
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6 votes

Short answer: No. Any site purporting to have a list of domains mapped to IP addresses won't be 100% accurate and it's based on what was seen, not what exists. Unless you have access to the name ...

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

Since DHCP Discovery broadcasts initially and to avoid the need for ip-helper addresses, the L3 switch where your users or servers connect is generally the better spot for DHCP. You didn't mention ...

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How are two "ip helper-address" statements handled?
6 votes

Your ip-helper is the correct way to do this for redundancy and is the recommended method. The DHCPDiscovery (broadcast) gets picked up by the ip-helper and then unicasts to each DHCP server with the ...

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Incoming/Outgoing Traffic of LACP trunk
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5 votes

Your SNMP index may not match your port number. On some platforms, the indexes are not even persistent across reloads unless configured to be. I'd expect to find an interface speed of 2Gbps in your ...

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How can I connect two different locations through our ISP?
5 votes

IPSec VPN Virtual Private Network (VPN) over the Internet with IPSec protocols for authentication and encryption. Using a Firewall w/VPN is typical here. A hub-and-spoke model is generally deployed....

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How to find a list of devices connected to my network (IP's and MACs)
5 votes

DHCP Snooping for both the L3 IP and L2 MAC addresses if you seek to just identify your clients using dynamic addresses. This is used for security to block rogue DHCP servers and only allow packets ...

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Is it possible to remotely influence BGP localpref?
5 votes

The best you can usually do is look for communities with your provider that allow you to indicate prepends per peer of your provider. This assumes your provider has such communities and has the ...

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Cisco: monitoring users input
5 votes

TACACS+ is the preferred method to log CLI commands at any enable level. See the AAA and TACACS commands for configuration. There's open source software if you don't have or can't afford Cisco ACS ...

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How to extensively test an ethernet switch
4 votes

Judging by your switch, I'd say you don't have the budget for a real ethernet tester like those from Fluke Networks. Your switch is Layer 2 (L2) only and doesn't support routing, so you'd need an ...

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Is a VPN concentrator different from a VPN gateway?
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4 votes

Yes, though they are often used interchangeably. A VPN gateway may refer to a router, firewall, or VPN Concentrator that provides Virtual Private Networks. A VPN Concentrator is a dedicated [VPN ...

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Cisco Prime / 5508 WLC captive portals
4 votes

Not directly on the WLC, but using Cisco ACS, ISE or other RADIUS server, you can set the captive URL using the url-redirect value of the cisco-av-pair RADIUS attribute. This overrides the WLC ...

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How can the SIP timeout on a Cisco PIX be increased for the REGISTER transaction type?
Accepted answer
4 votes

After further research, looks like this is Cisco bug CSCei29494 though I see no fixed release. An ASA 5515-X running 9.1(2) shows the same 0:03:00 timeout, also apparently not configurable, though it ...

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Block usage of proxy server
4 votes

One way that won't be well-received is to provide a locked-down proxy inside your network and block all inside-out tcp/80 traffic except for that proxy. Your clients won't get web access unless they ...

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What behavior results from both ip dhcp pool and ip helper-address?
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4 votes

Is the DHCP addresses given from the helper? or from the local pool? You would get two possible DHCPOffer's from the device's internal DHCP pool and the DHCP server defined by the helper-address, but ...

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TCP Vegas algorithm description
Accepted answer
4 votes

This is my interpretation of TCP Vegas for your questions. Other scholars here could correct this or augment it. Q1. "The change of the modified slow-start is that the window is increased every ...

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Where to properly put the DHCP server?
4 votes

A pair of DHCP servers could easily handle many different subnets and provides redundancy. Separate VLANs for wired and wireless in this small network requires a little more setup, but I'd say it is ...

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