+ Reply to Thread
Results 1 to 6 of 6
  1. Senior Member
    Join Date
    Oct 2005
    Posts
    1,030

    Certifications
    CCNP (R&S/Voice), CCDP, CCIP, VCP, NCDA, MCSE, CCNA Security
    #1

    Default 3750 MAC Address Table

    I am labbing MAC flooding attacks on my 3750 and came across a seemingly weird issue. When the table is full and I can see unicast frames on ports they weren't intended for 'show mac address-table count' still shows space for 40 more addresses. Are there some "slots" reserved on 3750s? I thought they might be for static entries, but after adding a few statics it seems that is not the case. I tried the same thing on a 3550 and it shows no address space available.

    I upgraded to the latest IOS (12.2(53)SE2) with the same results.

    Code:
    Switch#show mac address-table count
    
    Mac Entries for Vlan 1:
    ---------------------------
    Dynamic Address Count  : 5960
    Static  Address Count  : 0
    Total Mac Addresses    : 5960
    
    Total Mac Address Space Available: 40
    Any insight is appreciated.
    Reply With Quote Quote  

  2. SS -->
  3. Senior Member ConstantlyLearning's Avatar
    Join Date
    Dec 2006
    Location
    Dublin, Ireland
    Posts
    444

    Certifications
    JNCIA-JunOS, CCNP, CCNA-Security, CCNA, CCENT, CWNA, JNCIA-FWV, Security+, Network+, A+, MCP, MCSA, ITIL Foundation V3
    #2
    Same bug in the two IOS version's you've tried?

    Did a bit of googling and saw a couple of "show mac address-table count" outputs from 3750's that were exhausted and showed "Total Mac Address Space Available: 0"
    Reply With Quote Quote  

  4. Senior Member
    Join Date
    Oct 2005
    Posts
    1,030

    Certifications
    CCNP (R&S/Voice), CCDP, CCIP, VCP, NCDA, MCSE, CCNA Security
    #3
    Yeah, the versions were pretty close together. I suppose I should find an older version and give it a try.

    Thanks
    Last edited by kalebksp; 07-31-2010 at 11:31 PM.
    Reply With Quote Quote  

  5. Senior Member
    Join Date
    Oct 2005
    Posts
    1,030

    Certifications
    CCNP (R&S/Voice), CCDP, CCIP, VCP, NCDA, MCSE, CCNA Security
    #4
    Yep, I switched to an older IOS and total space available goes to zero.
    Reply With Quote Quote  

  6. Senior Member
    Join Date
    Mar 2007
    Posts
    12,308
    #5
    What were you using perform the flooding?
    Reply With Quote Quote  

  7. Senior Member
    Join Date
    Oct 2005
    Posts
    1,030

    Certifications
    CCNP (R&S/Voice), CCDP, CCIP, VCP, NCDA, MCSE, CCNA Security
    #6
    I was using macof.
    Reply With Quote Quote  

+ Reply to Thread

Social Networking & Bookmarks