AIX 5L Configuring TCP/IP (Unit 07): Network Control

Unit Objectives
Discuss Virtual IP Addressing
Describe Multipath Routing
Explain Dead Gateway Detection
Configure Network Options

Virtual IP Address
Virtual IP Address
Network Adapter

Application availability issue
Application binds to a virtual address
Can be brought up or down without affecting real interfaces fileset

Note: If you have two adapters and one fails, then you can switch to using the second adapter without having to change the Virtual IP Address and socket that the application is bound to.

Create Virtual IP Address
# smit mkinetvi
Add a Virtual IP Address Interface

Multipath Routing
Host –> tr0, tr1 –> Gateway –> Destination Host
\____>eno –> Gateway –> /

no -o
no -o udp_pmtu_discover=0
Load balancing among Gateways
Load balancing among interfaces on same network
Alternate backup for failed paths

Cost Attribute
Host –> tr0 –cost=0 –> Gateway –> Destination Host
\–>eno –cost=0 –> Gateway –> /

Route cost metric (hopcount)
User configurable

no -o
creates a host specific route
network route

User-configurable Cost
# netstat -C

hopcount Parameter
# route add -if pp0 -hopcount 25
Interface specific
Cost versus user configuration cost
PMTU issue (cloned routes)

Dead Gateway Detection
Gateway status checked, if down switch to backup gateway
TCP – Retries to send, if no response the raise the cost which forces the use of an alternate route
ARP – Address Resolution Protocol – Flush the cache every 20 minutes, rebroadcast, if no response then raise the cost of that route forcing the use of the alternate route

Note: There is a time delay in detecting that the route is down as TCP retries and ARP rebroadcasts. However, they are trading off adding an extra load to the system.

Passive DGD
Uses TCP and ARP for detection
Low overhead
Does not Ping
Monitors traffic

Active DGD
# route change default -active_dgd
Meets availability requirements
Ping checks status
Per route basis
Network traffic issue

# netstat -mC

Quality of Service
If a gateway having multiple inputs and fewer outputs begins to be congested then policies can be made that will give certain packets priority service. A file transfer can wait but a video stream may not.
Network Bandwidth
Regulate traffic
Manage bandwidth
Policy based
Specify policy priority

Unit Summary
Virtual IP provides connection protection
Multipath routing allows more than one route to same destination
Passive Dead Gateway Detection for minimal overhead
Active Dead Gateway Detection for maxiumum availability
Quality of Service to regulate traffic

Exercise 7 – Configuring Network Options
sys2 as Client
sys3 as Server

Make sure that it is turned off
no -a | grep pmtu
route -f (flush the routes)
route add 0
ping sys4

Use virtual address on server for availability
smitty mkinetvi (vi for virtual interface)
Add a Virtual Interface
Interface: vi0

netstat -in (list interfaces)
netstat -rn (list routing)
ifconfig vi0 (show interface)

Check host name resolution
cat /etc/hosts
vi /etc/hosts sysvi3

hosts sysvi3 (check name resolution)

Setup router
netstat -rn

sys98r (router system)
netstat -rn
route add
netstat -rn

ping sysvi3
ping -c1 -R sysvi3

Multipath Routing
route add sysvi3 sys98r -if en0 -hopcount 25
route add sysvi3 ppp3 -if pp0 -hopcount 25
Note: Load balanced at 25 each route.
netstat -rn (shows two routes available)

netstat -C (display net cost)
ping -c1 -R sysvi3 (Test load balance)
ping -c1 -R sysvi3 (Alternates between routes)

ifconfig en0 down (take down en0 interface)
ping -c1 -R sysvi3 (Test load balance)
ping -c1 -R sysvi3 (Fails)
ping -c1 -R sysvi3 (Test load balance)
ping -c1 -R sysvi3 (Fails)

netstat -C (cost has not changed)

route change sysvi3 sys98r -active_dgd (doesn’t work very well)
route delete sysvi3 sys98r
route add sysvi3 sys98r -if en0 -hopcount 25 – active_dgd

netstat -C (A flag shows active gateway detection, cost = MAX)
ping -c1 -R sysvi3
ping -c1 -R sysvi3 (Same route used not the other)

ifconfig en0 up (bring up en0 interface up)
netstat -C (Cost of en0 is back to cost of 25)
ping will now alternate

ifconfig pp0 down
ping tries to alternate
pp0 is does not have active detection turn on
ifconfig pp0 up (now alternates)

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