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Category Archives: Networking

How to stop a Cisco ASA from replying to ICMP traffic from outside

Monday, August 22, 2011

Use the following command: icmp deny any outside

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Problem With Bonding and Packet Loss on Red Hat Enterprise Linux 3

Tuesday, March 1, 2011

We moved a blade server running Red Hat Enterprise Linux 3 from one enclosure to another. The old enclosure had Nortel switches, the new enclosure had Cisco switches. After moving the server we noticed connectivity problems. Looking at the switches it appeared that the server’s MAC address was moving between the different switches. There were [...]

Also filed in Linux and Unix | | Comments (0)

Slow Upload Performance

Wednesday, January 19, 2011

We were having issues where some PCs had slow upload performance over the WAN. The WAN link was a E3 (34Mbps) with round trip latency of around 50ms and was not congested. When uploading to SharePoint, some PCs would upload at between 150 and 250 KBps. Otherwise identical PCs would upload at over 1MBps. The [...]

Also filed in SharePoint, Windows | | Comments (0)

Flexible NetFlow through an IPSec VPN Tunnel

Monday, August 9, 2010

As of IOS 12.4(20)T Cisco routers can send NetFlow data through an IPSec VPN tunnel. The flow exporter just needs to be configured with the output-features option. According to Configuring Data Export for Cisco IOS Flexible NetFlow with Flow Exporters this option “Enables sending export packets using QoS and encryption”. For example: flow exporter NFSVR [...]

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Poor Voice Quality, Inbound Calls Work, Outbound Calls Don’t on BRI

Monday, August 9, 2010

I had an issue the other day when we replaced an ISDN PRI interface with a BRI. I reconfigured the voice gateway and had inbound calls working – albeit a fair bit of static. However, I could not get outbound calls to go via the BRI interface. I had debugging on for isdn q931 and [...]

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Different MTU Settings on a Cisco 877 Router

Tuesday, April 20, 2010

I have a remote site on an ADSL connection using a Cisco 877 router. There’s an IPSec VPN back to my location. They connection speed is very good: Download Speed (kbps): 23410 Upload Speed (kbps): 1017 The ADSL router was configured with pretty typical MTU and MSS settings (probably copied off the Internet): interface Vlan1 [...]

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DynDNS and Cisco 877 Router

Sunday, December 6, 2009

I had a couple of issues getting DynDNS working on a Cisco router. The first issue was: how do I type a question mark within an IOS configuration command? Normally, when you type ? IOS responds with its command help. This is obviously a problem when you’re trying to enter a URL that contains a [...]

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My mnemonic for the seven layer OSI model

Monday, October 8, 2007

All Application People Presentation Should Session Taste Transport Nobby’s Network Delicious Data Link Peanuts Physical

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Configuring L2TP Support on a Cisco ISR Router

Saturday, September 1, 2007

Instructions I consulted a number of sites on the Internet when I was attempting to configure L2TP on a Cisco router. I found many people with the same issues I had but no complete solution. In the end, my problem was that I needed an access list (see access-list 130 below). Below is an example [...]

Also filed in Cisco, IOS, IPSec, L2TP, Router | | Comments (0)