Network Management
Download
Report
Transcript Network Management
Network Management And
Debugging
WeeSan Lee <[email protected]>
http://www.cs.ucr.edu/~weesan/cs183/
Roadmap
Interface Configuration
Route Configuration
Network Debugging
Network Topology
The
Internet
192.168.0.0/24
.2
Router VM
.1
Host VM
.2
10.0.0.0/24
Interface Configuration (Host VM)
We will need:
IP Address
Netmask
255.255.255.0
Broadcast
10.0.0.2
10.0.0.255
Gateway
10.0.0.1
Usually
10.0.0.0 - network
10.0.0.255 - broadcast
Interface Configuration (Router VM)
Use ifconfig command
$ ifconfig eth1 10.0.0.1 netmask 255.255.255.0
$ ifconfig eth1
eth1 Link encap:Ethernet HWaddr 00:C0:F0:3C:43:82
inet addr:10.0.0.1 Bcast:10.0.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:659988 errors:1 dropped:0 overruns:0 frame:0
TX packets:1016790 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:73459942 (70.0 Mb) TX bytes:1201693614 (1146.0 Mb)
Interrupt:10 Base address:0xd880
To bring the interface eth1 down or up via ifconfig command
$ ifconfig eth1 down
$ ifconfig eth1 up
Interface Configuration (Router VM)
Edit /etc/sysconfig/network-scripts/ifcfg-eth1
To bring up the interface eth1 via ifup script
DEVICE=eth1
ONBOOT=yes
#BOOTPROTO=dhcp
IPADDR=10.0.0.1
NETMASK=255.255.255.0
BROADCAST=10.0.0.255
$ ifup eth1
To bring down the interface eth1 via ifdown script
$ ifdown eth1
IP Aliasing
A way to assign multiple IP addresses on the
same interface
$ ifconfig eth1:0 10.0.0.3 netmask 255.255.255.0
$ ifconfig eth1:1 10.0.0.4 netmask 255.255.255.0
Why?
We could experiment new services w/out new HW
We could replace problematic HW with IP aliasing
on a healthy machine temporary
Route Configuration (Router VM)
Default routes
Usually added by route command
To remove a default route
$ route add default gw 192.168.0.1
$ route del default gw 192.168.0.1
To make it persistent, edit /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=host1
DOMAINNAME=weesan.com
GATEWAY=192.168.0.1
Route Configuration (Router VM)
$ netstat -rn
Kernel IP routing table
Destination Gateway
192.168.0.0 0.0.0.0
169.254.0.0 0.0.0.0
0.0.0.0
192.168.0.1
Genmask
255.255.255.0
255.255.0.0
0.0.0.0
Flags MSS Window irtt Iface
U
0
0
0 eth0
U
0
0
0 eth0
UG 0
0
0 eth0
Route Configuration (Router VM)
Static routes
Usually added by ifconfig command
$ route add -net 10.0.0.0 netmask 255.255.255.0 eth1
$ route del -net 10.0.0.0 netmask 255.255.255.0 eth1
Edit /etc/sysconfig/static-routes
eth1 net 10.0.0.0 netmask 255.255.255.0
Route Configuration (Router VM)
$ netstat -rn
Kernel IP routing table
Destination Gateway
10.0.0.0
0.0.0.0
192.168.0.0 0.0.0.0
169.254.0.0 0.0.0.0
0.0.0.0
192.168.0.1
Genmask
255.255.255.0
255.255.255.0
255.255.0.0
0.0.0.0
Flags MSS Window irtt Iface
U
0
0
0 eth1
U
0
0
0 eth0
U
0
0
0 eth0
UG 0
0
0 eth0
Enable IP Forwarding (Router VM)
$ echo "1" > /proc/sys/net/ipv4/ip_forward
To make it persistent, edit /etc/sysctl.conf
Change net.ipv4.ip_forward to 1
Network Debugging
Can be tricky
Start from one component and work your way
through
Recommend procedures (bottom-up)
Always check power first
Check the LED on the devices
Check connectivity, use tools like ping, traceroute,
tcpdump, etc
Verify application protocol, use telnet
ping
Send ICMP-REQUEST and expect ICMP-REPLY
$ ping 10.0.0.1
PING 10.0.0.1 (10.0.0.1) 56(84) bytes of data.
64 bytes from 10.0.0.1: icmp_seq=1 ttl=64 time=1.18 ms
64 bytes from 10.0.0.1: icmp_seq=2 ttl=64 time=1.57 ms
64 bytes from 10.0.0.1: icmp_seq=3 ttl=64 time=1.03 ms
--- 10.0.0.1 ping statistics --3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 1.036/1.263/1.572/0.228 ms
ping
Start from known next hop
Not always works for remote hosts
For example, eon.cs.ucr.edu drops ICMP packets
traceroute
Send UDP packets to remote host with TTL 1, 2, 3, …
$ weesan@delta-1:~> traceroute www.google.com
traceroute: Warning: www.google.com has multiple addresses; using 72.14.253.99
traceroute to www.l.google.com (72.14.253.99), 30 hops max, 38 byte packets
1 138.23.211.1 (138.23.211.1) 0.286 ms 0.278 ms 0.353 ms
2 c6513telecom--te-9-4.ucr.edu (138.23.3.105) 25.070 ms 20.486 ms 1.064 ms
3 c6509telecom--te-3-3.ucr.edu (138.23.3.26) 0.384 ms 0.381 ms 0.361 ms
4 riv-dc1.riv-dc1--ucr.cenic.net (137.164.24.121) 0.311 ms 0.235 ms 0.225 ms
5 dc-lax-dc1--riv-dc1-pos.cenic.net (137.164.22.228) 1.457 ms 1.459 ms 1.446 ms
6 ***
…
11 po-in-f99.google.com (72.14.253.99) 31.902 ms 30.762 ms 30.745 ms
tcpdump
Originally written by Van Jacobson
$ tcpdump
$ tcpdump -i eth0
$ tcpdump host eon
$ tcpdump src net 10.0.0.0/24 and dst port 80
$ tcpdump -vvv
$ man tcpdump
Reference
LAH
Ch 12: TCP/IP Networking
Ch 13: Routing
Ch 19: Network Management And Debugging