VLAN Tagging, You're It!

Let's continue on from the previous post with a discussion of VLAN Tagging. VLAN tagging is a mechanism to denote a way to tell networking devices what virtual network to ship a particular packet to and from. Many times, networking devices can be geographically distant. With VLANs interfaces can "appear" to be part of the same network. To configure vlan tagging for our interface from the last session:

1. root@routername#configure
2. edit interfaces fe-2/0/1
3. set vlan-tagging
4. Next we add a VLAN ID of 100 on our logical unit 0: root@routername#set unit 0 vlan-id 100
5. show our new configuration with the show command

Caution! Juniper routers DO NOT have a default VLAN! Every VLAN must be explicitly configured. Many switches have a default VLAN of 1. Make sure to configure a vlan-id of 1 for connectivity.

It is a common "best practice" to have th einterface unit number be the same as the VLAN ID, so we change the unit number with the rename unit 0 to unit 100 command. Let's activate the change with root@routername#commit To retest for connectivity, issue run ping 10.10.20.121 count 3 When it succeeds, we can view our interface with run show interfaces terse fe-2/0/1

Now let us move on to T1 interfaces...

T1 is a very extensively used signaling method in North America. For point-to-point links on Juniper devices, the default encapsulation is PPP. This differs with many other vendor's equipment whose default encapsulation is Cisco HDLC (There is a standard HDLC protocol, but it did not have multi-protocol support. Cisco's HDLC implementation is "officially" proprietary, but the workings are well known and supported by many vendors.) Here is a configuration example for a T1 interface.

1. edit interfaces t1-0/0/2
2. set encapsulation cisco-hdlc
3. set unit 0 family inet address 10.10.20.122/24
4. commit

Acronyms of the Moment:

DTE: Data Terminal Equipment

DCE: Data-circuit Terminal Equipment

"Serial is not Breakfast!"

Serial interfaces have a variety of physical forms such as, V.35, X.21, and EIA 530. V.35 is most commonly seen in the United States and X.21 is common in Japan. All serial interfaces define their connection in terms of a DCE and a DTE. DCE devices provide clocking signals, encoding, and signal conversion to the DTE. Normally routers will default to DTE mode by default until wired up and a DCE(female cable) is detected.

Let's view our DCE status with the run show interfaces se-1/0/0 extensive find "serial media" command. The DTE/DCE detection can be found in the local mode field.

Note: Proper care must be taken to configure the correct clock mode. Without proper clocking, the link status will be considered "down."

Under the [serial-options] in the [edit interfaces] hierarchy a clocking-mode may be set. The default is internal or loop timed, and the clock rate is 8Mhz

"Serial with Frame Relay"

Frame Relay is a Layer 2 enapsulation method that allows a LAN connection via a Wide Area Network Connection (WAN) to a Frame Relay node. Frame Relay uses Permanent Virtual Circuit (PVC) tunnelling over an Internet Service Provider's infrastructure to provide the LAN's connectivity.

Acronyms of the Moment:

DSL: Digital Subscriber Line

DLCI: Data Link Circuit Identifier

With the widespread emergence of other broadband technologies such as DSL and IP networks, Frame Relay is mostly seen in rural areas as a cheap "always on" service. To establish a Frame Relay connection, the frame-relay encapsualtion is set, along with a local circuit identifier for the PVC in the form of a DLCI.

1. edit interface se-1/0/0
2. set unit 645 family inet address 172.17.24.130/30
3. set encapsulation frame-relay
4. set dlci 645
5. commit

Note: No routers were harmed in the making of this blog ;-)