Guide to IP Layer Network Administration with Linux

List of Examples

1.1. Sample ifconfig output

1.2. Testing reachability of a locally connected host with ping

1.3. Testing reachability of non-local hosts

1.4. Sample routing table with a static route

1.5. ifconfig and route output before the change

1.6. Bringing down a network interface with ifconfig

1.7. Bringing up an Ethernet interface with ifconfig

1.8. Adding a default route with route

1.9. Adding a static route with route

1.10. Removing a static network route and adding a static host route

2.1. ARP conversation captured with tcpdump

2.2. Gratuitous ARP reply frames

2.3. Unsolicited ARP request frames

2.4. Duplicate Address Detection with ARP

2.5. ARP cache listings with arp and ip neighbor

2.6. ARP cache timeout

2.7. ARP flux

2.8. Correction of ARP flux with conf/$DEV/arp_filter

2.9. Correction of ARP flux with net/$DEV/hidden

2.10. Proxy ARP Network Diagram

2.11. Bringing up a VLAN interface

2.12. Link aggregation bonding

2.13. High availability bonding

4.1. Classes of IP addresses

4.2. Using ipcalc to display IP information

4.3. Identifying the locally connected networks with route

4.4. Routing Selection Algorithm in Pseudo-code

4.5. Listing the Routing Policy Database (RPDB)

4.6. Typical content of /etc/iproute2/rt_tables

4.7. unicast route types

4.8. broadcast route types

4.9. local route types

4.10. nat route types

4.11. unreachable route types

4.12. prohibit route types

4.13. blackhole route types

4.14. throw route types

4.15. Kernel maintenance of the local routing table

4.16. unicast rule type

4.17. nat rule type

4.18. unreachable rule type

4.19. prohibit rule type

4.20. blackhole rule type

4.21. ICMP Redirect on the Wire

5.1. Stateless NAT Packet Capture

5.2. Basic commands to create a stateless NAT

5.3. Conditional Stateless NAT (not performing NAT for a specified destination network)

5.4. Using an ipchains packet filter with stateless NAT

5.5. Using DNAT for all protocols (and ports) on one IP

5.6. Using DNAT for a single port

5.7. Simulating full NAT with SNAT and DNAT

7.1. Blocking a destination and using the REJECT target, cf. Example D.17, “Adding a prohibit route with route add”

10.1. Multiple Outbound Internet links, part I; ip route

10.2. Multiple Outbound Internet links, part II; iptables

10.3. Multiple Outbound Internet links, part III; ip rule

10.4. Multiple Internet links, inbound traffic; using iproute2 only

11.1. Proxy ARP SysV initialization script

11.2. Proxy ARP configuration file

11.3. Static NAT SysV initialization script

11.4. Static NAT configuration file

B.1. Displaying the arp table with arp

B.2. Adding arp table entries with arp

B.3. Deleting arp table entries with arp

B.4. Displaying reachability of an IP on the local Ethernet with arping

B.5. Duplicate Address Detection with arping

B.6. Using ip link show

B.7. Using ip link set to change device flags

B.8. Deactivating a link layer device with ip link set

B.9. Activating a link layer device with ip link set

B.10. Using ip link set to change device flags

B.11. Changing the device name with ip link set

B.12. Changing broadcast and hardware addresses with ip link set

B.13. Displaying the ARP cache with ip neighbor show

B.14. Displaying the ARP cache on an interface with ip neighbor show

B.15. Displaying the ARP cache for a particular network with ip neighbor show

B.16. Entering a permanent entry into the ARP cache with ip neighbor add

B.17. Entering a proxy ARP entry with ip neighbor add proxy

B.18. Altering an entry in the ARP cache with ip neighbor change

B.19. Removing an entry from the ARP cache with ip neighbor del

B.20. Removing learned entries from the ARP cache with ip neighbor flush

B.21. Detecting link layer status with mii-tool

B.22. Specifying Ethernet port speeds with mii-tool --advertise

B.23. Forcing Ethernet port speed with mii-tool --force

C.1. Viewing interface information with ifconfig

C.2. Bringing down an interface with ifconfig

C.3. Bringing up an interface with ifconfig

C.4. Changing MTU with ifconfig

C.5. Setting interface flags with ifconfig

C.6. Displaying IP information with ip address

C.7. Adding IP addresses to an interface with ip address

C.8. Removing IP addresses from interfaces with ip address

C.9. Removing all IPs on an interface with ip address flush

D.1. Viewing a simple routing table with route

D.2. Viewing a complex routing table with route

D.3. Viewing the routing cache with route

D.4. Adding a static route to a network route add

D.5. Adding a static route to a host with route add

D.6. Adding a static route to a host on the same media with route add

D.7. Setting the default route with route

D.8. An alternate method of setting the default route with route

D.9. Removing a static host route with route del

D.10. Removing the default route with route del

D.11. Viewing the main routing table with ip route show

D.12. Viewing the local routing table with ip route show table local

D.13. Viewing a routing table with ip route show table

D.14. Displaying the routing cache with ip route show cache

D.15. Displaying statistics from the routing cache with ip -s route show cache

D.16. Adding a static route to a network with route add, cf. Example D.4, “Adding a static route to a network route add”

D.17. Adding a prohibit route with route add

D.18. Using from in a routing command with route add

D.19. Using src in a routing command with route add

D.20. Setting the default route with ip route add default

D.21. Creating a NAT route for a single IP with ip route add nat

D.22. Creating a NAT route for an entire network with ip route add nat

D.23. Removing routes with ip route del

D.24. Altering existing routes with ip route change

D.25. Testing routing tables with ip route get

D.26. Removing a specific route and emptying a routing table with ip route flush

D.27. Emptying the routing cache with ip route flush cache

D.28. Displaying the RPDB with ip rule show

D.29. Creating a simple entry in the RPDB with ip rule add

D.30. Creating a complex entry in the RPDB with ip rule add

D.31. Creating a NAT rule with ip rule add nat

D.32. Creating a NAT rule for an entire network with ip rule add nat

D.33. Removing a NAT rule for an entire network with ip rule del nat

F.1. Simple use of nc

F.2. Specifying timeout with nc

F.3. Specifying source address with nc

F.4. Using nc as a server

F.5. Delaying a stream with nc

F.6. Using nc with UDP

F.7. Simple use of socat

F.8. Using socat with proxy connect

F.9. Using socat perform SSL

F.10. Connecting one end of socat to a file descriptor

F.11. Connecting socat to a serial line

F.12. Using a PTY with socat

F.13. Executing a command with socat

F.14. Connecting one socat to another one

F.15. Simple use of tcpclient

F.16. Specifying the local port which tcpclient should request

F.17. Specifying the local IP to which tcpclient should bind

F.18. IP redirection with xinetd

F.19. Publishing a service with xinetd

F.20. Simple use of tcpserver

F.21. Specifying a CDB for tcpserver

F.22. Limiting the number of concurrently accept TCP sessions under tcpserver

F.23. Specifying a UID for tcpserver's spawned processes

F.24. Redirecting a TCP port with redir

F.25. Running redir in transparent mode

F.26. Running redir from another TCP server

F.27. Specifying a source address for redir's client side

G.1. Using ping to test reachability

G.2. Using ping to specify number of packets to send

G.3. Using ping to specify number of packets to send

G.4. Using ping to stress a network

G.5. Using ping to stress a network with large packets

G.6. Recording a network route with ping

G.7. Setting the TTL on a ping packet

G.8. Setting ToS for a diagnostic ping

G.9. Specifying a source address for ping

G.10. Simple usage of traceroute

G.11. Displaying IP socket status with netstat

G.12. Displaying IP socket status details with netstat

G.13. Displaying the main routing table with netstat

G.14. Displaying the routing cache with netstat

G.15. Displaying the masquerading table with netstat

G.16. Viewing an ARP broadcast request and reply with tcpdump

G.17. Viewing a gratuitous ARP packet with tcpdump

G.18. Viewing unicast ARP packets with tcpdump

G.19. tcpdump reporting port unreachable

G.20. tcpdump reporting host unreachable

G.21. tcpdump reporting net unreachable

G.22. Monitoring TCP window sizes with tcpdump

G.23. Examining TCP flags with tcpdump

G.24. Examining TCP acknowledgement numbers with tcpdump

G.25. Writing tcpdump data to a file

G.26. Reading tcpdump data from a file

G.27. Causing tcpdump to use a line buffer

G.28. Understanding fragmentation as reported by tcpdump

G.29. Specifying interface with tcpdump

G.30. Timestamp related options to tcpdump