DNS

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Two types of IP addresses IPV4 and IPV6

IPV4 - 32 bit field has over 4 billion addresses possible.

it was not assumed that internet will grow this much while creation of IPV4 scheme.

So ipv6 which has 128 bit field and has 340 undecillion addresses.

.com .edu is top level domain name

.gov.us is second level domain name.

controlled by IANA(Internet Assined nunmbers authority), and has root zone database.which db of top level domains.

Domains Registrars make sure there are no duplicates.

Every l domains as records in who.is db.

NS records - name server records . These are used by top level domains servers to direct traffic to the CDN servers which contains the authoritative DNS records.

hellorpout53gurus..com

ISP - .com- ns records- soa(in our case it is amazon) - and then the all the record set..

A(address) record = name - ip.

CName - one alias for the A record.

A CName can't be used for "cloudguru.com"(Zone apex record), although can be used for www.cloudguru.com so Alias record came into practise.

ELBs do not have predefined IPV4 addresses, we resolve them by DNS name.

naked domain name -> to elb, use alias and that to dns name.

always use alias over cname.

SOA - is onformation strored in DDNS zone baout that zzone.

Each zone cantians one sinfgle SOA record.

DNS zone is part of doamisn for which SDNS server is resposible.

Alias record is dynamic by AWS. so a.com -> elb.

if elb ip changes , AWS will update it dynamically.

MX records ,for mail service.

PTR, for reverse lookup.

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Different routings

das

Simple routing , Weighted routing.

With SImple routing we can have only one A record.

Weight - relative to other weights..