Currently viewing the category: "Cisco-security"

Cisco: Small escape leading to non-functional NAT

By On January 20, 2010 · 2 Comments

I have seen that a lot of people is using search engines to look after terms like “NAT: failed to allocate address for…” or “NAT: address not stolen for…” asking for help in regard to a non-functional NAT. Of course I skipped the cases when the solution was obvious and clear like wrong NAT configuration, [...]

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Cisco: DoS protection using TCP Intercept

By On May 19, 2009 · 2 Comments

Every now and then, all network engineers have to deal with some kind of network attack.  Usually, the attack does not target the network devices, but the machines that provide services (e.g. www, database hosting…), because it’s more easy to find on the Internet a script that is probing port 80 for example, which by [...]

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Cisco: How to use reflexive access-list and why they are useful

By On March 30, 2009 · 4 Comments

Reflexive access-list are one of the method that help us achive firewall functionality with a router hardware. The other methods that serve to the same purpose are Context-Based Access Control (CBAC) and TCP Intercept. For an introduction to CBAC with example please check my older post

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Cisco: How to configure privileges for local users

By On March 2, 2009 · 3 Comments

I believe that all of you are familiar with privilege levels (0-15) on Cisco IOS. The most useful for network engineers is level 15 and the highest one as it will allow you full access to all IOS features, but in most networks only a few persons have this privilege level. In my opinion is [...]

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Cisco: FWSM CPU stress test how-to

By On February 6, 2009 · 2 Comments

Sometime ago I had to do a stress test for a Cisco FWSM (Firewall Service Module) to see how the resources are consumed and if some potential traffic can temporarly affect the behavior of this device. For those of you who have don’t know what is a Cisco FWSM, here comes the definition: “Cisco Firewall [...]

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Cisco: Use CBAC to achieve firewall functionality on router device

By On January 19, 2009 · 4 Comments

Sometimes, because of cost saving usually, the network engineers are forced to use a Cisco router as a firewall (instead of Cisco PIX or ASA). One of the big difference between router and firewall devices is that the ports have different characteristics. If on routers, ports are permitting by default traffic of any packets in [...]

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Cisco: Layer 1 link failure detection

By On January 12, 2009 · Leave a Comment

It has been a while since I didn’t post anything here, but it was holidays and I used that time to relax and rest after a year of work. Following this idea I wish you all “Happy New Year” and all the best in 2009.

Today I planned to write about something easy to implement [...]

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Cisco: Spoof detection

By On November 24, 2008 · 2 Comments

Spoofing is a kind of network attack to compromise your network security with the intention of traffic capture which will enable an attacker to get access to confidential data. Usually a spoof attach is associated with IP spoofing, which means that the source IP of the packet which arrive to your device has been changed [...]

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