Document ID: 17600
Questions
Introduction
I have a Frame Relay connection to my ISP and some clients cannot get to my network reliably. Line quality has checked out, what could be wrong?
I have a Frame Relay connection to my ISP and I cannot seem to transfer files over a certain size?
Do I have to define a maintenance protocol in my router when I use a Frame Relay connection?
What do I need if I want a Frame Relay connection to the Internet?
Do Compatible Systems routers support un-numbered Frame Relay?
Related Information
Introduction
This document answers some of the most frequently asked questions about Frame Relay.
Refer to Cisco Technical Tips Conventions for more information on document conventions.
Q. I have a Frame Relay connection to my ISP and some clients cannot get to my network reliably. Line quality has checked out, what could be wrong?
A. Make sure that your static route points to the correct REMOTE WAN IP address, not simply "WAN A". When you point your static route to the WAN port only, or the incorrect remote WAN IP address, it can result in fragmentation problems that exhibit this behavior.
Incorrect:
Destination Mask Gateway Metric Rip 0.0.0.0 0.0.0.0 WAN B 1Correct, where 168.142.10.12 is the far side of the Frame Relay connection:
Destination Mask Gateway Metric Rip 0.0.0.0 0.0.0.0 168.142.10.12 1
Q. I have a Frame Relay connection to my ISP and I cannot seem to transfer files over a certain size?
A. First, check your static route configuration. If you point your static route to the WAN port only, or the incorrect remote WAN IP address, this can result in fragmentation problems (see the first question).
Next, check your configuration for the Maximum Transmission Unit (MTU) size. The MTU is typically set for 1500, which is the Ethernet standard. If the router encounters a large file that must be fragmented, it splits it into 1500 byte size chunks. After the headers and trailers for IP and Frame Relay get added, these can be more than 1500 bytes long. It is then necessary to configure a larger MTU in the router. The MTU must be the same on both sides of the Frame Relay. If they are different, that might also cause your problem.
Q. Do I have to define a maintenance protocol in my router when I use a Frame Relay connection?
A. The maintenance protocol is used to send link status and virtual circuit information between Frame Relay switches and other devices (such as routers) that communicate with them. In some cases, the switch autosenses the maintenance protocol that has been set by default in the router. Typically, the telco tells you which maintenance protocol to use or that it is not required for your connection.
You can identify which maintenance protocol being used, if any, by viewing your Frame Relay configuration.
AnnexD is an ANSI standard and is the most commonly used standard in the United states. AnnexD is the default maintenance protocol.
AnnexA is a CCITT European standard.
LMI was developed by a vendor consortium and is also known as the "consortium" management interface specification. It is still used by some carriers in the United States.
Static is a method for using WAN broadcast media (for example, satellite ground stations) to emulate a Frame Relay network. Do not use this setting for normal Frame Relay switch communications.
Q. What do I need if I want a Frame Relay connection to the Internet?
A. This is the bare bones information that you need from an ISP.
IP Number Block for LAN—This can be an entire Class C network or a subnet (see IP 101 for an explanation of Class C networks and subnets).
IP number for WAN Port—Your WAN port must be numbered with an IP address for Frame Relay. The ISP supplies this address. It must be on a different network or subnet than your LAN. The ISP also has the WAN port numbered. Your WAN port address and the ISP WAN port address must be on the same network or subnet.
Routing Protocol—The ISP router may listen for RIP packets from your network to determine how to route to you. If not, the ISP needs to set a static route in the router to your network. This route must be broadcast by the IPS's router to the Internet so that you can access the Internet. If you use a subnet of a Class C, RIP does not carry the subnet information and the ISP router needs a route to your subnet.
DLCI Number—Your WAN port must have a DLCI number. Your router is configured with a DLCI database, which contains the DLCI number and the ISP WAN port address. This defines the PVC through the Frame Relay cloud.
DNS Addresses—The ISP has a Domain Name Server for you to access, if you do not have one. The DNS name and address must be entered in the TCP/IP software setup on your workstations.
Q. Do Compatible Systems routers support un-numbered Frame Relay?
A. Yes.
With the release of software, v4.4.10, support for IP un-numbered Frame Relay is included. Read the Compatible Systems Tech Note Un-numbered Frame Relay to determine the additional keywords that are needed to configure the WAN port of a router to work on an IP un-numbered Frame Relay connection. A sample configuration is also included.
Related Information
| Updated: Apr 12, 2002 | Document ID: 17600 |