hsrp packet:
http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094afd.shtml
http://www.booches.nl/2008/07/25/secure-hsrp-configuration/
http://www.networksorcery.com/enp/protocol/hsrp.htm
http://farm4.static.flickr.com/3264/2439892475_12e75cedc1_m.jpg
http://packetlife.net/blog/2008/oct/27/hijacking-hsrp/
http://networkninja.co.za/cisco-systems/hot-standy-router-protocol-hsrp/
https://supportforums.cisco.com/docs/DOC-3558;jsessionid=F0069337AA7B569279E561C974DCB04F.node0
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http://wiki.nil.com/Cheatsheets
http://wiki.nil.com/Category:Utilities
http://wiki.nil.com/Category:MPLS_VPN
http://wiki.nil.com/QoS_Policing_in_Cisco_IOS
http://wiki.nil.com/Traffic_shaping_in_Cisco_IOS
http://wiki.nil.com/Configuration_maker
http://wiki.nil.com/Multi-VRF_based_VPN
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http://blog.ioshints.info
http://packetlife.net
http://www.networksorcery.com
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IPSEC
http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a00800ef7ba.shtml
http://it.toolbox.com/wiki/index.php/Cisco_Ipsec_VPN
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Serial loop tests
http://www.cisco.com/en/US/tech/tk713/tk628/technologies_tech_note09186a00800a754b.shtml#ext_ping
http://itknowledgeexchange.techtarget.com/itanswers/how-to-check-the-loop-in-cisco-switch/
http://www.sadikhov.com/forum/index.php?showtopic=78839
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Cisco QoS – CoS
http://www.cisco.com/en/US/tech/tk543/tk757/technologies_tech_note09186a00800949f2.shtml
http://www.cisco.com/en/US/docs/ios/12_2/qos/configuration/guide/qcfpoli_ps1835_TSD_Products_Configuration_Guide_Chapter.html
http://www.cisco.com/en/US/products/sw/cscowork/ps2064/products_user_guide_chapter09186a0080080946.html
http://www.cisco.com/en/US/tech/tk543/tk545/technologies_tech_note09186a0080094acb.shtml
http://www.cisco.com/en/US/docs/ios/12_2/qos/configuration/guide/qcfpolsh.html