28.1, how to solve the problem of slow-speed access to the website:
To test himself as a user, if it is no problem to think from the customer's point of view
If there's a problem
ping website
Pass, without loss:
http service problems to check whether the service stopped, the service cpu, io high (top), the port website (nmap wangzhi -p 80), firewall, (curl www.baidu.com: the equivalent of browser access)
Website to buy bandwidth full view through traffic monitoring
Individual users their own problems, line and website bandwidth line does not match the user
By commissioning website url
Database problem, the problem of storage server
Tong, loss:
Room Bandwidth instability, unstable line
Unreasonable:
traceroute -d www.baidu.com: each routing node of the investigation
28.2, how to solve the problem within the LAN without Internet access:
ping
ping www.baidu.com
If it passes:
It may be the reason the browser;
If unreasonable, ping the gateway:
If the ping of: checking whether normal dns
If the ping fails: ping other hosts
Barrier: View ip settings, network card driver, the physical link
If you pass: it may be the Internet gateway to prevent
Assist the investigation:
Other people may look at the Internet, ip address conflict, arp virus, the switch is broken, not over a large area network
28.3, network tools:
[Root @ centos6 ~] # tcpdump icmp # capture tool
nmap: scanning tool
28.3.1, DNS tools:
[root@centos6 ~]# host www.baidu.com
www.baidu.com is an alias for www.a.shifen.com.
www.a.shifen.com has address 115.239.211.112
www.a.shifen.com has address 115.239.210.27
[root@centos6 ~]# nslookup
> www.baidu.com
Server: 114.114.114.114
Address: 114.114.114.114#53
Non-authoritative answer:
www.baidu.com canonical name = www.a.shifen.com.
Name: www.a.shifen.com
Address: 115.239.211.112
Name: www.a.shifen.com
Address: 115.239.210.27
28.4、dns域名解析过程：
[root@centos6 ~]# dig @8.8.8.8 www.baidu.com +trace
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.37.rc1.el6 <<>> @8.8.8.8 www.baidu.com +trace
; (1 server found)
;; global options: +cmd
. 194151 IN NS e.root-servers.net.
. 194151 IN NS a.root-servers.net.
. 194151 IN NS g.root-servers.net.
. 194151 IN NS h.root-servers.net.
. 194151 IN NS b.root-servers.net.
. 194151 IN NS l.root-servers.net.
. 194151 IN NS i.root-servers.net.
. 194151 IN NS d.root-servers.net.
. 194151 IN NS k.root-servers.net.
. 194151 IN NS f.root-servers.net.
. 194151 IN NS j.root-servers.net.
. 194151 IN NS c.root-servers.net.
. 194151 IN NS m.root-servers.net.
;; Received 228 bytes from 8.8.8.8#53(8.8.8.8) in 277 ms
com. 172800 IN NS a.gtld-servers.net.
com. 172800 IN NS b.gtld-servers.net.
com. 172800 IN NS c.gtld-servers.net.
com. 172800 IN NS d.gtld-servers.net.
com. 172800 IN NS e.gtld-servers.net.
com. 172800 IN NS f.gtld-servers.net.
com. 172800 IN NS g.gtld-servers.net.
com. 172800 IN NS h.gtld-servers.net.
com. 172800 IN NS i.gtld-servers.net.
com. 172800 IN NS j.gtld-servers.net.
com. 172800 IN NS k.gtld-servers.net.
com. 172800 IN NS l.gtld-servers.net.
com. 172800 IN NS m.gtld-servers.net.
;; Received 491 bytes from 199.7.91.13#53(199.7.91.13) in 537 ms
baidu.com. 172800 IN NS dns.baidu.com.
baidu.com. 172800 IN NS ns2.baidu.com.
baidu.com. 172800 IN NS ns3.baidu.com.
baidu.com. 172800 IN NS ns4.baidu.com.
baidu.com. 172800 IN NS ns7.baidu.com.
;; Received 201 bytes from 192.42.93.30#53(192.42.93.30) in 320 ms
www.baidu.com. 1200 IN CNAME www.a.shifen.com.
a.shifen.com. 1200 IN NS ns2.a.shifen.com.
a.shifen.com. 1200 IN NS ns1.a.shifen.com.
a.shifen.com. 1200 IN NS ns3.a.shifen.com.
a.shifen.com. 1200 IN NS ns5.a.shifen.com.
a.shifen.com. 1200 IN NS ns4.a.shifen.com.
;; Received 228 bytes from 220.181.37.10#53(220.181.37.10) in 36 ms