Category: Cisco
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CablesAndKits Clearance…I Couldn’t Resist
I grabbed three 836s for $4.80 each! These dudes are technically DSL modems, so as far as that goes, they are dead to me. On the inside, it has a 4 port switch that you can assign VLANs. These guys will make great IPSLA nodes for line quality testing…and for $4.80 each…forget about it! CNK…
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Layer 2 Security – Protect You and Your Users From Attack
Before your access lists or firewall rules comes layer 2(L2). This is the Data link layer where your MAC addressing lives. Why do we need to protect L2…? Man in the middle attacks happen via L2 Rogue DHCP on a single segment DHCP server starvation attack ARP attacks against your switches Lets hit these guys…
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Cisco Callmanager External Phone Numeber Masking
The external phone number mask is a method to present whatever caller id (CID) info you want to the outside world. As in, when I call you from my Cisco phone my number shows up as 555-5555, because my phone number mask is set to 555-5555. There are multiple places you can affect the number…
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Cisco BGP Troubleshooting
Some times there is nothing better for trouble shooting that a nice process tree. Cisco has a great set of them here. My favorite is “Troubleshoot missing routes”: Always remember that when you check your filters that you are checking your prefix list AND your AS-path filters! Issue the “show ip bgp sum” command to…
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Cisco Policy Based Routing – Violate Route Table – Send Some Traffic One Way and Everything Else The Other
The idea in this scenario is as follows: You have two ISPs. You want all of your user’s web traffic to exit and enter ISP1 and everything else to exit and enter ISP2. You also need the ISP connections to backup each other in the case of a failure of either. Here’s our lovely diagram…
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Cisco – Multisite Single Cluster Call Manager 4.1 Design
On the heels of my CIPT test (call manager test), I’ve completely redesigned from the ground up our call manager configuration. I’ve changed the way the system works pretty much completely…hehe. I spent a good bit of time putting together the Visio, so I figured I would share it with you guys, and also explain…
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Cisco – Troubleshoot T1 PRI
So we have been turning up a new PRI lately and had HUGE amounts of trouble with it. It all came down to the fact that the telco told us to use the wrong PRI type, but that’s the fix…the fun was in the journey. Here are the steps we took to resolve the issue.…