| Exam 300-115 | Question id=1383 | Layer 2 Technologies |
Refer to the exhibit.
switch#show etherchannel summary
Flags: D - down P - bundled in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3 S - Layer2
U - in use f - failed to allocate aggregator
M - not in use, minimum links not met
u - unsuitable for bundling
w - waiting to be aggregated
d - default port
Number of channel-groups in use: 3
Number of aggregators: 3
Group Port-channel Protocol Ports
------+-------------+-----------+--------------------------------
12 Po12(SU) - Fa0/13(P) Fa0/14(P) Fa0/15(P)
13 Po13(SU) - Fa0/16(P) Fa0/17(P) Fa0/18(P)
14 Po14(SU) - Fa0/19(P) Fa0/20(P) Fa0/21(P)
switch#show interfaces trunk
Port Mode Encapsulation Status Native vlan
Po12 desirable n-isl trunking 1
Po13 desirable n-isl trunking 1
Po14 desirable n-isl trunking 1
Port Vlans allowed on trunk
Po12 1-4094
Po13 1-4094
Po14 1-4094
Which EtherChannel negotiation protocol is configured on the interface f0/13 – f0/15?
| A. |
Link Combination Control Protocol | |
| B. |
Port Aggregation Protocol | |
| C. |
Port Combination Protocol | |
| D. |
Link Aggregation Control Protocol |
PAgP modes are off, auto, desirable, and on. Only the combinations auto-desirable, desirable-desirable, and on-on will allow a channel to be formed.
1. on: PAgP will not run. The channel is forced to come up.
2. off: PAgP will not run. The channel is forced to remain down.
3. auto: PAgP is running passively. The formation of a channel is desired; however, it is not initiated.
4. desirable: PAgP is running actively. The formation of a channel is desired and initiated.
The Link Aggregate Control Protocol (LACP) trunking supports four modes of operation:
* On: The link aggregation is forced to be formed without any LACP negotiation .In other words, the switch neither sends the LACP packet nor processes any inbound LACP packet. This is similar to the on state for PAgP.
* Off: The link aggregation is not formed. We do not send or understand the LACP packet. This is similar to the off state for PAgP.
* Passive: The switch does not initiate the channel but does understand inbound LACP packets. The peer (in active state) initiates negotiation (when it sends out an LACP packet) which we receive and answer, eventually to form the aggregation channel with the peer. This is similar to the auto mode in PAgP.
* Active: We can form an aggregate link and initiate the negotiation. The link aggregate is formed if the other end runs in LACP active or passive mode. This is similar to the desirable mode of PAgP.
In this example, we see that fa 0/13, fa0/14, and fa0/15 are all in Port Channel 12, which is operating in desirable mode, which is only a PAgP mode.