Step 5: Ping the Fast Ethernet or Gigabit Ethernet Interface

Purpose

Use the ping command to verify the loopback connection.

Action

To send ping packets from the Ethernet interface, use the following JUNOS CLI operational mode command:

user@host> ping remote-IP-address bypass-routing interface (fe-fpc/pic/port | 
ge-fpc/pic/port) count 100 rapid

Sample Output

user@router> ping 10.108.120.2 bypass-routing interface ge-7/2/1 count 100 rapid 

PING 10.108.120.2 (10.108.120.2): 56 data bytes

36 bytes from 10.108.120.1: Time to live exceeded

Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst

 4  5  00 0054 e871   0 0000  01  01 cc5c 10.108.120.1  10.108.120.2 

.36 bytes from 10.108.120.1: Time to live exceeded

Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst

 4  5  00 0054 e874   0 0000  01  01 cc59 10.108.120.1  10.108.120.2 

.36 bytes from 10.108.120.1: Time to live exceeded

Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst

 4  5  00 0054 e878   0 0000  01  01 cc55 10.108.120.1  10.108.120.2 

.36 bytes from 10.108.120.1: Time to live exceeded

Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst

 4  5  00 0054 e87c   0 0000  01  01 cc51 10.108.120.1  10.108.120.2 

.36 bytes from 10.108.120.1: Time to live exceeded

Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst

 4  5  00 0054 e880   0 0000  01  01 cc4d 10.108.120.1  10.108.120.2 

.36 bytes from 10.108.120.1: Time to live exceeded

Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst

 4  5  00 0054 e884   0 0000  01  01 cc49 10.108.120.1  10.108.120.2 

.36 bytes from 10.108.120.1: Time to live exceeded

What It Means

As the packet is looped over the link, you receive a series of TTL exceeded messages. These messages are received because the ping packets are looped repeatedly between the router and the physical loopback until the IP TTL expires.