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What Layer does Frame Relay work on?
Layer 2(Data Link)
What is the formula to figure out how many connections are needed for a fully meshed topology?
(N*(N-1))/2
What is a VC? What does it do?
Virtual circuit. Can connect to multiple locations/devices with one physical circuit.
How many types of VC's are there, and what are they?
2
PVC(permanent VC)
SVC(semi-permanent VC)
What is an LMI? What is its function?
Local Management Interface- This defines how the DTE (the router or other Frame Relay device) interacts with the DCE (the Frame Relay switch). A KeepAlive Mechanism for VCs
What is an DLCI? What is its function?
Data Link Connection Identifier - This value is used to uniquely identify each VC on a physical interface
What is an CIR? What is its function?
This is the average data rate, measured over a fixed period of time, that the carrier guarantees for a VC.
How many different LMI's are there, and what are they?
3
The Gang of Four
ANSI's Annex D
ITU-T's Q.933 Annex A
Cisco has default timers for its status enquiry and full status update messages, what are they?
Status enquiry messages are sent every 10 seconds, by default. Every sixth message is a full status update message.
what are the Default DLCI#'s for each LMI type?
ANSI Annex D = 0
ITU-T Annex A = 0
Gang of Four(Cisco) = 1023
What is the DE bit and what happens when the bit is set?
DE = Discard Eligible
This bit is set when traffic is sent at a rate between Bc(commited burst rate) and Be(excessive burst rate), the carrier will allow the packet to travel if the network isn't congested. If the network gets congested the DE marked packets are the first to drop.
What does BECN mean, and what does it do?
BECN = Backward Explicit Congestion Notification
This value is set by the destination DTE (Frame Relay device) in the header of the Frame Relay frame to indicate congestion (from the source to the destination) to the source of the Frame Relay frames (the source DTE, the router).
What does FECN mean, and what does it do?
FECN = Forward Explicit Congestion Notification
This value in the Frame Relay frame header is set by the carrier switch (typically) to indicate congestion inside the carrier network to the destination device at the end of the VC; the carrier may be doing this to your traffic as it is on its way to its destination.
What does a router(DTE) do when it recieves a Frame Relay pack with the BECN bit on?
It slows down the data rate on the VC(Virtual circuit)
What does a router(DTE) do when it recieves a Frame Relay pack with the FECN bit on?
It reply's to the packet as normal but it turns on the BECN bit.
What commands are used to set the data link layer encapsulation type to Frame Relay
Router (config)# interface serial [slot_#/]port_#

Router (config-if)# encapsulation frame-relay [cisco|ietf]
How many different types of Frame Relay encapsulation are there, and what are they?
2
cisco- default if not declared otherwise
ietf-most providers use this
What commands are used to configure LMI?
Router(config)# interface serial [slot_#/]port_#

Router(config-if)# frame-relay lmi-type ansi|cisco|q933a

FYI - Cisco routers with an IOS version greater that 11.2 can autosense LMI Type
What commands can you use to troubleshoot LMI, and what does each show you?
show interfaces - THis command will show encapsulation type, LMI type and some LMI stats.
show frame-relay lmi - More detailed listing of LMI stats than what show interfaces.
debug frame-relay lmi - This command will show you real-time LMI messages recieved and sent by router.
What commands are used to manually configure DLCI numbers to layer 3 addresses?
Router (config)# interface serial [slot_#/]port_#

Router (config-if)# frame-relay map protocol_name destination_address local_dlci_#
[broadcast] [ietf | cisco]

FYI - Broadcast and ietf/cisco are optional parameters

Broadcast - Set if you want to allow broadcasts over the PVC. For instance routing protocol(RIPv2, EIGRP, OSPF) updates.

ietf/cisco - This parameter allows you to set encapsulation type per interface if not staticaly set.
How many VC(Virtual Circuit) status's are there, and what do they mean?
3

Active - The VC between both Frame Relay DTEs is up and operational.

Inactive - The VC between your Frame Relay DTE and DCE is up and operational, but something is wrong with the connection between your connected Frame Relay switch and the destination DTE.

Deleted - You are not receiving any LMI messages from the Frame Relay switch for a local VC.
What commands are used to configure DLCI numbers to dynamically determine layer 3 addresses?
There is no configuration needed. The router can determine the Layer 3 address by doing an inverse arp, the router won't preform the inverse arp until the LMI status message has been sent, so the router won't transfer data for at least 60 seconds.
How do you disable or enable inverse-arp?
Router (config)# interface serial [slot_#/]port_#

Router (config-if)# [no] frame-relay inverse-arp [protocol_name] [DLCI_#]
What command would you use to determine what PVCs are terminated at the router?
Router# show frame-relay pvc

FYI - If you are only interested in the info for one PVC you could put the DLCI number at the end of the command.
Example :
Router# show frame-relay pvc 100
How would you determine what layer 3 address is assigned to a certian DLCI number?
Router# show frame-relay map

FYI - below is output example
Serial0 (up): ip 192.168.2.2 dlci 32(0x20, 0x1C80), dynamic,
Broadcast, CISCO, status defined, active

In this output, one PVC has a local DLCI of 32. At the end of this PVC is a router with an IP address of 192.168.2.2. Notice that this information was learned via Inverse ARP (dynamic), local broadcasts and multicasts are allowed, the default frame type is cisco, and the status of the VC is active