Google Networking Best Practices for Large Deployments - Manual (Page 19)

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Chapter 6
Network Configuration
Chapter 6
Summary
This section includes details on how to optimize your network for Google Apps. This includes
information on Google’s IPv4 addresses, protocols used, routing suggestions, proxy server
configuration options, and DNS configuration. Use this information as a guide when
configuring your network, and as a reference for what types of requests Google Apps clients
will make to Google servers.
Network Addressing and Protocols
Google IPv4 Addresses
Google Apps exists in a multi-tenant server environment that includes both Google Apps and
consumer accounts. Therefore, Google Apps shares the same IPv4 address space as Google
consumer services. For example, Google Docs servers could use the same IPv4 address
space as Picasa Web. In addition, a specific IPv4 address for a Google hostname, such as
mail.google.com
or
docs. google.com
, might be serving both Google Apps and consumer
users at the same time.
For any Google hostname, such as
mail.google.com
or
docs.google.com
, the IPv4 address is
not static and is valid only for its time-to-live (TTL) value returned in the DNS lookup of the
hostname.
For example, if we query the A record for
mail.google.com
, several results are returned:
% dig a mail.google.com +ttl
;; ANSWER SECTION:
mail.google.com. 68665 IN CNAME googlemail.l.google.com.
googlemail.l.google.com. 152 IN A 74.125.225.86
googlemail.l.google.com. 152 IN A 74.125.225.87
googlemail.l.google.com. 152 IN A 74.125.225.85