Juniper Networks J-Series manual Using Services Router Diagnostic Tools, Diagnostic Terms

Chapter 12

Using Services Router Diagnostic Tools

J-series Services Routers support a suite of J-Web tools and CLI operational mode commands for evaluating system health and performance. Diagnostic tools and commands test the connectivity and reachability of hosts in the network.

This chapter contains the following topics. For complete descriptions of CLI operational mode commands, see the JUNOS System Basics and Services Command Reference, the JUNOS Interfaces Command Reference, and the JUNOS Routing Protocols and Policies Command Reference.

■Diagnostic Terms on page 209

■Diagnostic Tools Overview on page 210

■Before You Begin on page 215

■Pinging Hosts from the J-Web Interface on page 216

■Checking MPLS Connections from the J-Web Interface on page 219

■Tracing Unicast Routes from the J-Web Interface on page 223

■Capturing and Viewing Packets with the J-Web Interface on page 226

■Using CLI Diagnostic Commands on page 230

Diagnostic Terms

Before diagnosing J-series Services Routers, become familiar with the terms defined in Table 104 on page 209.

Table 104: J-series Diagnostic Terms

Term	Definition
Don't Fragment (DF) bit	Bit in the IP header that instructs routers not to fragment a packet. You might set this bit if the
	destination host cannot reassemble the packet or if you want to test the path maximum
	transmission unit (MTU) for a destination host.
routing instance	Collection of routing tables, interfaces, and routing protocol interfaces. The set of interfaces
	belongs to the routing tables, and the routing protocol parameters control the information in the
	routing tables.
loose source routing	Option in the IP header used to route a packet based on information supplied by the source. A
	gateway or host must route the packet using the routers specified by this information, but the
	packet can use other routers along the way.

Diagnostic Terms ■ 209