Category Archives: Cisco

Cisco – Understanding Unicast Reverse Path Forwarding (URPF)

Understanding Unicast Reverse Path Forwarding Unicast RPF Examples Cisco IOS Devices An important consideration for deployment is that Cisco Express Forwarding switching must be enabled for Unicast RPF to function. This command has been enabled by default as of IOS … Continue reading

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IP Fragmentation

NIL – The Never-Ending Story of IP Fragmentation. Listing 1 Permitting PMTUD-related ICMP packets in an extended ip access-list permit icmp any any packet-too-big deny icmp any any fragments Clear the don’t fragment bit for UDP traffic ip access-list extended … Continue reading

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Cisco – Access Control Lists and IP Fragments

Access Control Lists and IP Fragments access-list 100 permit tcp any host 171.16.23.1 eq 80 access-list 100 deny ip any any access-list 101 deny ip any host 171.16.23.1 fragments access-list 101 permit tcp any host 171.16.23.1 eq 80 access-list 101 … Continue reading

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Incorrect IP Fragmentation for GRE Over IPSec Configurations

Incorrect IP Fragmentation for GRE Over IPSec Configurations R1#show crypto ipsec sa | in mtu|interface|peer|spi R2#show process cpu | include CPU|IP Input R2#show ip traffic | in reassemble|fragment R1(config)# crypto ipsec fragmentation after-encryption

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Netowrk Labs

Netowrk Labs.

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Packet Capture packets at IOS Cisco router

Capture packets at IOS Cisco router or finally we have a sniffer    

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ISAKMP DPD and Invalid SPI Recovery

ISAKMP DPD and Invalid SPI Recovery.

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