Using DMVPN with Linux


DMVPN is a very intelligent combination of IPsec, GRE and NHRP. Many Thanks to the Guys at Cisco, Christoph, Frederick and all other.

This week i discovered “opennhrp” on sourceforge.

It took me a minute or two to have a VM with debian up and the needed tools installed.

I used VMWare with a bridged ethernet interface for testing, installed debian 4.0 netinstall iso and upgraded to sid / testing, so i got Kernel Version 2.6.26-1-686.

Then downloaded ipsec-tools-0.8-alpha20090126.tar.bz2 from the site. you have to install some libs and tools to build ipsec tools, like kernel headers and so on:-) and done some configure and make stuff.

I went to make opennhrp, well all done with out a problem to here.

Next i configured racoon and ipsec-tools and opennhrp like this:

   /etc/ipsec-tools.conf 
   #!/usr/sbin/setkey -f
   spdflush;
   spdadd 0.0.0.0/0 0.0.0.0/0 gre -P out ipsec esp/transport//require;
   spdadd 0.0.0.0/0 0.0.0.0/0 gre -P in ipsec esp/transport//require;

   /etc/racoon/racoon.conf 
   path pre_shared_key "/etc/racoon/psk.txt";
   remote anonymous {
      exchange_mode main,aggressive;
      lifetime time 24 hour;
      # nat_traversal on;
      script "/etc/opennhrp/racoon-ph1down.sh" phase1_down;
      proposal {
         encryption_algorithm 3des;
         hash_algorithm sha1;
         authentication_method pre_shared_key;
         dh_group 5;
      }
   }
   sainfo anonymous {
      lifetime time 12 hour;
      encryption_algorithm 3des, blowfish 448, rijndael;
      authentication_algorithm hmac_sha1, hmac_md5;
      compression_algorithm deflate;
   }

   /etc/racoon/psk.txt
   10.2.0.90 1234

   /etc/opennhrp/opennhrp.conf
   interface gre1
      map 172.255.255.1/24 10.2.0.90 register cisco
      cisco-authentication 1234
      shortcut

No get the Tunnel UP:

   ip tunnel add gre1 mode gre key 1234 ttl 64
   ip addr add 172.255.255.2/24 dev gre1
   ip tunnel change gre1 local 10.0.81.115
   ip link set gre1 up

Now its time to get on the other side.

We are using a Cisco 1812 with c181x-advsecurityk9-mz.124-15.T7.bin running.

   crypto isakmp policy 10
      encr 3des
      authentication pre-share
      group 5
   !
   crypto isakmp key 1234 address 0.0.0.0 0.0.0.0
   !
   crypto ipsec transform-set TRANSFORMSET_3 esp-3des esp-sha-hmac
      mode transport
   !
   crypto ipsec profile Profile3
      set transform-set TRANSFORMSET_3
   !
   interface Tunnel888
      ip address 172.255.255.1 255.255.255.0
      no ip redirects
      no ip unreachables
      no ip proxy-arp
      ip mtu 1400
      ip flow ingress
      ip nhrp authentication 1234
      ip nhrp map multicast dynamic
      ip nhrp network-id 10064
      ip nhrp holdtime 360
      ip nhrp max-send 200 every 10
      ip route-cache same-interface
      ip tcp adjust-mss 1350
      load-interval 30
      tunnel source 10.2.0.90
      tunnel mode gre multipoint
      tunnel key 1234
      tunnel protection ipsec profile Profile3

and viola

   Router# sh dmvpn interface tunnel 888
   Load for five secs: 8%/3%; one minute: 9%; five minutes: 10%
   Time source is NTP, 22:14:22.148 CET Sat Feb 14 2009
   Legend: Attrb --> S - Static, D - Dynamic, I - Incompletea
   N - NATed, L - Local, X - No Socket
   # Ent --> Number of NHRP entries with same NBMA peer
   Tunnel888, Type:Hub, NHRP Peers:1,
   # Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb
   ----- --------------- --------------- ----- -------- -----
   1 10.0.81.115 172.255.255.2 UP never D

   Router# ping 172.255.255.2
   Type escape sequence to abort.
   Sending 5, 100-byte ICMP Echos to 172.255.255.2, timeout is 2 seconds:
   !!!!!
   Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/8 ms

this looks great:-)
Many thanks Timo for doing such a impressiv work. I like the cisco for they impressiv boxes and i also like opensource software.

— edit February 15, 2009 at 12:09 am —

I found after a while no packets traveling, the nhrp registration had gone on the cisco side may be holdtimers differ so added “holding-time 360″ to the opennhrp.conf , a opennhrpctl purge fixed the problem.

 

Thanks to Patrick

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