ARP resolution IP to MAC address

[vinchez]

On Pg No. 332 (CCNA Study Guide Sixth Edition), o/p of arp -a command shows,

c:\>arp -a
Interface: 172.16.10.2 --- 0x3
Internet Address Physical Address Type
172.16.10.1 00-15-05-06-31-b0 Dynamic

On Pg No. 334, o/p of sh ip arp command shows,

Lab_A#sh ip arp
Protocol Address Age(min) Hardware Addr Type Interface
Internet 172.160.20.1 - 00d0.58ad.05f4 ARPA Ethernet0
Internet 172.160.20.2 3 0030.9492.a5dd ARPA Ethernet0
Internet 172.160.10.1 - 00d0.58ad.06aa ARPA Ethernet0
Internet 172.160.10.2 12 0030.9492.a4ac ARPA Ethernet0

Now, why does resolution of IP address 172.16.10.1 show two different MAC addresses in ARP cache table of router & host. I mean arp -a shows 00-15-05-06-31-b0 as Physical Address & sh ip arp shows 00d0.58ad.06aa as Hardware Address?

Or should I ask whether Physical Address & Hardware Address are two different entities? and if at all they are, how they differ?


* Trivial question - Why notation of Hardware address & Physical address (. dot / - Hyphen notation and grouping of digits) are different???