Introduction- As we are already aware, the web pages that we access on a daily basis works based on domain names and DNS server is the one which converts them to IP addresses and provide a seamless browsing experience for users. But what if there is only one DNS server configured and it becomes unreachable?
End user's perception is that the PC is no longer online, even though it has a valid IP address and route that would provide internet access.
Feature Notes- By design, on Instant Access Point only two DNS server IP addresses can be configured from GUI. There are situations, where a corporate design might want to allocate multiple DNS addresses to users. Corporates do this for many reason, couple of them are below:
- To have redundant DNS Server availability to users.
- To configure load balancing of huge DNS queries that come in from user subnets.
Environment- This article applies to all versions of Aruba InstantOS versions.
Network Topology- Network Topology:
- Instant architecture works on be a flat topology so that access points can form a cluster.
Configuration Steps- Configuration from IAP side is almost nil as the IP addresses for multiple DNS server addresses needs to be received from DHCP server on Access Points vlan.
This is how it works:
# IAP gets an IP address from DHCP server in the network on the management vlan
# Within the offer that the IAP receives from DHCP server, also needs to be included are all the IP addresses for DNS servers.
# Once IAP receives these IP addresses in offer, it would assign the same to the VC assigned subnet internally
Therefore, any wireless client connected to VC assigned SSID, would also receive all the DNS server IP addresses as part of DNS server configuration within the dhcp offer.
Verification- The "show dhcp-allocation" command on IAP would verify if the VC subnet has DNS addresses configured, to offer multiple addresses to clients:
IAP# show dhcp-allocation
43460 00:10:18:a9:7e:27 172.31.99.226 3333 KK-Desk-PC2 01:00:10:18:a9:7e:27 ---->>>>> Client obtained IP address
Below is the sample DHCP pool from Aruba Controller:
ip dhcp pool vlan200
dns-server 10.1.1.50 10.1.1.51 10.1.1.52 10.1.1.53 10.1.1.54 10.1.1.55 10.1.1.56 10.1.1.57
network 172.16.200.0 255.255.255.0