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First of all, may I welcome you to my site. My name is Chris and I'm from the UK and work as a Systems Engineer for Cisco. This blog was initially created to post up my subnetting technique but has now got more stuff to do with attaining Cisco certifications. Either way I really hope that the content is sufficent for your needs and I look forward to hearing your feedback. If you find that the content really helps you please feel free to donate using the PayPal link on the right.
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CCIE Study - Written v4 Chapters 1 to 3 - 22/02/10
Tuesday 22 February 2011
Well I've learned lots actually, or more accurately put, I remembered lots of stuff that I had forgotten. Stupid stuff that I should have known right off the bat but slipped the mind.
Etherchannel
Cisco recommends for PAgP that both ends of the link be configured as Desirable.
Ethernet Basics
802.3ab defines GigabitEthernet over UTP whereas 802.3z defines GigabitEthernet over Fibre. 802.3u defines FastEthernet.
MAC addresses are in canonical format which means that the most significant bit is on the right. Take the first two hexidecimal values from a MAC address and convert them to binary to give you an 8-bit string. The Individual/Group bit (I/G) is the right-most bit (i.e. the most signficant bit). If that is set to 0 then the MAC address is a unicast. If it is set to 1 then the MAC address is a broadcast or multicast. The second right-most bit is the Universal/Local bit (U/L). If this is set to 0 then the MAC address has been assigned by the vendor. If it is set to 1 then the MAC address has been administratively assigned.
Q-in-Q
VPLS and EoMPLS offer alternatives to Q-in-Q.
Spanning Tree
If a switch does not have any trunks configured at boot time but has the "spanning-tree root primary" command issued the priority of the switch will go to 24576 which is 8192 less than the default priority of 32768. If a trunk link is then formed and a switch has a higher priority then it will become the root and not the one with the root primary macro.
If you want to configure BPDUGuard at interface level you must take off any interface-level PortFast configuration first.
If running 802.1D and the root port does not receive any BPDUs the switch will wait for the Max Age timer to expire (default 20 seconds) before using another port.
Port priority and port number when used as a tiebreaker are those on the advertising switch and not on the switch that receives the BPDU.
If a root port fails then switchover to an alternative port is almost immediate.
SPAN/RSPAN
Destination ports do not forward Layer 2 protocols such as CDP, DTP, VTP, and STP.
Up to 64 destination ports may be configured.
The monitor session number can range between 1 and 66.
VLANs
The only VLANs that can be pruned are VLANs 2-1001. VLANs 1, and 1002-1005 are not prune eligible and can never be deleted.
Posted byChris Bloomfield at 18:37
Labels: CCIE
