CCIE Pursuit Blog

September 26, 2007

Dynamips Blew Up On Me

Filed under: Dynamips,Home Lab — cciepursuit @ 7:07 pm
Tags: , , , ,

It was bound to happen.  I’ve been doing a lot of labs with Dynamips using 4 routers as 1 switch.  Today I started doing some BGP labs that required 5 routers.  Dynamips kept dumping its core (ewww!).  I tried to isolate the issue to a single router instance, but couldn’t do it.  I finally realized that as soon as the IOS loaded on the 6th device (7th if you count the Frame Relay switch) Dynamips would crash.  This is probably due to my laptop.  I only have 512Meg of RAM.  I had planned to drop 2 Gigs in it,  but Dynamips had been chugging along fine up until today.

I dropped the RAM on the Dynamips router instances from 128 to 96.  I was able to get all 6 devices up and working.  Success!!!  Well….until I tried to configure BGP that is:

r1(config)#router bgp 6
*Mar  1 00:42:45.707: %SYS-2-MALLOCFAIL: Memory allocation of 18360 bytes failed from 0x609B8D6C, alignment 0
Pool: Processor  Free: 6300  Cause: Not enough free memory
Alternate Pool: None  Free: 0  Cause: No Alternate pool

-Process= “Exec”, ipl= 0, pid= 3
-Traceback= 0x603F5B88 0x6053CC4C 0x60543434 0x609B8D74 0x60A08938 0x609B9DE0 0x
60798530 0x607999B8 0x60432DB0 0x60450578 0x604F164C 0x604F1630

I finally stripped the switch out of the equation (I just directly connected the couple of routers on Ethernet segments) and bumped the RAM back to 128.  I started each device one by one and then telnetted to it to make sure that it didn’t crash once the IOS was loaded.  I was finally able to get all 5 routers rockin and rollin with BGP and OSPF redistribution.

I put in an order for 2 gigs of RAM shortly after.  🙂


  1. You should split your virtual routers on 2 hypervisor instances to avoid this. I would advise not to exceed 5 or 6 routers per hypervisor.

    Comment by chris — September 30, 2007 @ 3:42 pm | Reply

  2. Hi Chris.

    Good tip. I’ll have to give that a try. The IE Dynamips lab .net file is shared over two hypervisor instances. Hopefully it’s an issue with the number of instances per hypervisor and not just my laptop running out of resources.

    Comment by cciepursuit — October 2, 2007 @ 3:11 pm | Reply

  3. Hi,

    I am using dynamips also for my CCIE Lab preparation and I am experiencing the same problems as you have.
    I used 2 IBM T60 (core solo and core duo) both with 2GB RAM. I ran 2 instances of dynamips and after so many scenarios configs/practices still crashes or got disconnected (maybe has something to do with Windows OS itself and maybe Linux is the solution, but given my limited time to install/configure, I sticked to Windows). I am so frustrated that I can’t finished the whole lab scenario.

    After I’ve done lots of readings in forums, I stumbled on someone who was able to connect live routers with dynamips. To make the story short, I managed to scramble/borrow some old routers (2500,1700, 2(2600)) and 1 unmanaged switch. I configured those borrowed equipment as BB1, BB2, BB3 and R6 (using internetworkexpert topology) and ran R1,2,3,4,5,SW1,SW2 on my TP.

    So far the experience is good and I am able to complete the lab scenario.

    Comment by ylizamar — November 6, 2007 @ 10:26 am | Reply

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