3.2. Lower Window
The lower window displays information about the other types of traffic on your network. The following protocols are detected internally:
User Datagram Protocol (UDP)
Internet Control Message Protocol (ICMP)
Open Shortest-Path First (OSPF)
Interior Gateway Routing Protocol (IGRP)
Interior Gateway Protocol (IGP)
Internet Group Management Protocol (IGMP)
General Routing Encapsulation (GRE)
Layer 2 Tunneling Protocol (L2TP)
IPSec AH and ESP protocols (IPSec AH and IPSec ESP)
Address Resolution Protocol (ARP)
Reverse Address Resolution Protocol (RARP)
Other IP protocols are looked up from the /etc/services file. If /etc/services doesn't contain information about that protocol, the protocol number is indicated.
Non-IP packets are indicated as Non-IP in the lower window.
 | Note |
|---|---|
The source and destination addresses for ARP and RARP entries are MAC addresses. Strictly speaking, ARP and RARP packets aren't IP packets, since they are not encapsulated in an IP datagram. They're just indicated because they are integral to proper IP operation on LANs. |
For all packets in the lower window, only the first IP fragment is indicated (since that contains the header of the IP-encapsulated protocol) but with no further information from the encapsulated protocol.
UDP packets are also displayed in address:port format while ICMP entries also contain the ICMP message type. For easier location, each type of protocol is color-coded (only on color terminals such as the Linux console).
- UDP
Red on White
- ICMP
Yellow on Blue
- OSPF
Black on Cyan
- IGRP
Bright white on Cyan
- IGP
Red on Cyan
- IGMP
Bright green on Blue
- GRE
Blue on white
- ARP
Bright white on Red
- RARP
Bright white on Red
- Other IP
Yellow on red
- Non-IP
Yellow on Red
The lower window can hold up to 512 entries. You can scroll the lower window by using the W key to move the Active indicator to it, and by using the Up and Down cursor keys. The lower window automatically scrolls every time a new entry is added, and either the first entry or last entry is visible. Upon reaching 512 entries, old entries are thrown out as new entries are added.
Some entries may be too long to completely fit in a screen line. You can use the Left and Right cursor keys to vertically scroll the lower window when it is marked Active. If your terminal can be resized (e.g. xterm), you may do so before starting IPTraf-ng.
Entries for packets received on LAN interfaces also include the source MAC address of the LAN host which delivered it. This behavior is enabled by turning on the Source MAC addrs in traffic monitor toggle in the Configure... menu.
3.2.1. Entry Details
In general, the entries in the lower window indicate the protocol, the IP datagram size (full frame size for non-IP, including ARP and RARP), the source address, the destination address, and the network interface the packet was detected on. However, some protocols have a little more information.
3.2.1.1. ICMP
ICMP entries are displayed in this format:
ICMP type [(subtype)] (size bytes) from source to destination [(src HWaddr srcMACaddress)] on interface
where type could be any of the following:
- echo req, echo rply
ICMP echo request and reply. Usually used by the ping program and other network monitoring and diagnostic program.
- dest unrch
ICMP destination unreachable. Something failed to reach its target. The dest unreach type is supplemented with a further indicator of the problem. Destination unreachable messages for TCP traffic causes the corresponding TCP entry in the upper window to be made available for reuse by new connections.
- redirct
ICMP redirect. Usually generated by a router to tell a host that a better gateway is available.
- src qnch
The ICMP source quench is used to stop a host from transmitting. It's a flow control mechanism for IP.
- time excd
Indicates a packet's time-to-live value expired before it got to its destination. Mostly happens if a destination is too far away. Also used by the traceroute program.
- router adv
ICMP router advertisement
- router sol
ICMP router solicitation
- timestmp req
ICMP timestamp request
- timestmp rep
ICMP timestamp reply
- info req
ICMP information request
- info rep
ICMP information reply
- addr mask req
ICMP address mask request
- addr mask rep
ICMP address mask reply
- param prob
ICMP parameter problem
- bad/unknown
An unrecognized ICMP packet was received, or the packet is corrupted.
The destination unreachable message also includes information on the type of error encountered. Here are the destination unreachable codes:
- ntwk
network unreachable
- host
host unreachable
- proto
protocol unreachable
- port
port unreachable
- pkt fltrd
packet filtered (normally by an access rule on a router or firewall)
- DF set
the packet has to be fragmented somewhere, but its don't fragment (DF) bit is set.
- src rte fail
source route failed
- src isltd
source isolated (obsolete)
- net comm denied
network communication denied
- host comm denied
host communication denied
- net unrch for TOS
network unreachable for specified IP type-of-service
- host unrch for TOS
host unreachable for specified IP type-of-service
- prec violtn
precedence violation
- prec cutoff
precedence cutoff
- dest net unkn
destination network unknown
- dest host unkn
destination network unknown
For more information on ICMP, see RFC 792.
3.2.1.2. OSPF
OSPF messages also include a little more information. The format of an OSPF message in the window is:
OSPF type (a=area r=router) (sizebytes) from source to destination [(src HWaddr srcMACaddress)] on interface
The type can be one of the following:
- hlo
OSPF hello. Hello messages establish OSPF communications and keep routers informed of each other's presence.
- DB desc
OSPF Database Description
- LSR
OSPF Link State Request
- LSU
OSPF Link State Update. Messages indicating the states of the OSPF network links
- LSA
OSPF Link State Acknowledgment
The entries in parentheses:
- a=area
The area number of the OSPF message
- r=router
The IP address of the router that generated the message. It is not necessarily the same as the source address of the encapsulating IP packet.
Many times, the destination addresses for OSPF packets are class D multicast addresses in standard dotted decimal notation or (if reverse lookup is enabled), hosts under the MCAST.NET domain. Such multicast addresses are defined as follows:
- 224.0.0.5 (OSPF-ALL.MCAST.NET)
OSPF all routers
- 224.0.0.6 (OSPF-DSIG.MCAST.NET)
OSPF all designated routers
See RFC 1247 for details on the OSPF protocol.