Update Cisco Catalyst Software

I had to update the software of a new Cisco Catalyst 4948 yesterday. As usual I did: copy tftp://<hostname>/<filename> bootflash: conf t boot system flash bootflash:<filename> exit reload But the switch ignored the new software image. During boot it said: Booting first image from bootflash Solution: The config-register was set to 0x2101 right out of …

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Pirelli Modem does allways NAT

When I restart my Pirelli modem it allways disconnects all TCP connections! After the connection table of the Pirelli is flushed (by rebooting) it sends a RST for the next packet of any TCP connection.Why doesn’t it simply forward this packet. Client and servers don’t care if a router on the way is rebooting. Pirelli …

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Pirelli doesn’t forward port 7070 correctly

Problem: Pirelli modem is not transparently routing traffic for tcp port 7070 and 554. I’m using a Pirelly VDSL modem at home in pure routing mode (no NAT, no QoS). When starting a TCP connection to port 7070 (or 554), the Pirelli modem answers the TCP SYN with SYNACK, then it tries to connect the …

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Multiple Routing Tables with IPTables

Challenge: You have a linux based firewall, which should forward all internal and external traffic of its connected clients through a VPN tunnel, and at the same time the traffic from the firewall itself should not go through the tunnel (e.g. the tunnel connection packets). Solution: There are lots of howtos for this probably. Here …

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BGP Looking Glass

If you like to search through the full Internet routing table from around the world, you can find some looking glasses at http://www.traceroute.org/ or http://www.routeviews.org/. e.g. Routeviews has telnet access to zebra servers (route-views.isc.routeviews.org,…)